(1)		Represents the maximum number of shares of ACI Worldwide, Inc. common stock that can be issued in the exchange offer and second-step merger.
(2)		Pursuant to Rule 457(c) and Rule 457(f) under the Securities Act, and solely for the purpose of calculating the registration fee, the market value of the securities to be received was calculated as the product of (i) 61,555,012 shares of S1 Corporation common stock (the sum of (x) 55,519,459 shares of S1 Corporation common stock outstanding as of August 18, 2011 and (y) 7,142,553 shares of S1 Corporation common stock issuable upon the exercise of outstanding options and warrants (as reported in the Proxy Statement on Schedule 14A filed by S1 Corporation on August 22, 2011), less (z) 1,107,000 shares of S1 Corporation common stock beneficially owned by ACI Worldwide, Inc.), and (ii) the average of the high and low sales prices of shares of S1 Corporation common stock as reported on the NASDAQ Stock Market on August 26, 2011 ($8.76), minus $381,641,074.40, the estimated maximum aggregate amount of cash to be paid by ACI Worldwide, Inc. in the exchange offer and second-step merger.
(3)		The amount of the filing fee, calculated in accordance with Rule 457(c) and Rule 457(f) under the Securities Act, equals 0.00011610 multiplied by the proposed maximum offering price.

 

     The information in this prospectus/offer to exchange may change. The registrant may not complete the Exchange Offer and issue these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus/offer to exchange is not an offer to sell these securities and ACI and Antelope Investment Co. LLC are not soliciting an offer to buy these securities in any state or jurisdiction in which such offer is not permitted.

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			Page
QUESTIONS AND ANSWERS ABOUT THE EXCHANGE OFFER			1
SUMMARY OF THE EXCHANGE OFFER			12
The Companies			12
The Exchange Offer			13
Reasons for the Exchange Offer			13
Conditions of the Exchange Offer			19
Ownership of ACI After the Exchange Offer			20
Comparative Market Price and Dividend Information			20
Interest of Executive Officers and Directors of ACI in the Exchange Offer			21
Source and Amount of Funds; Financing			22
Appraisal/Dissenters’ Rights			22
Certain Material Federal Income Tax Consequences			22
Accounting Treatment			23
Regulatory Approval and Status			23
Listing of ACI Shares to be Issued Pursuant to the Exchange Offer and the Second-Step Merger			24
Comparison of Stockholders’ Rights			24
Expiration Time of the Exchange Offer			24
Extension, Termination and Amendment			24
Procedure for Tendering Shares			25
Withdrawal Rights			25
Acceptance for Exchange and Exchange of S1 Shares; Delivery of Exchange Offer Consideration			25
Cash in Lieu of Fractional ACI Shares			26
Elections and Proration			26
Risk Factors			26
SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF ACI			27
SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF S1			29
SUMMARY SELECTED UNAUDITED PRO FORMA COMBINED FINANCIAL INFORMATION			31
HISTORICAL AND PRO FORMA PER SHARE INFORMATION			34
COMPARATIVE MARKET PRICE AND DIVIDEND INFORMATION			35
RISK FACTORS			37
Risk Factors Relating to the Exchange Offer and the Second-Step Merger			37
Risk Factors Relating to S1’s Businesses			40
Risk Factors Relating to ACI’s Businesses			40
Risk Factors Relating to ACI Following the Exchange Offer			40
THE COMPANIES			42

			Page
ACI			42
Offeror			42
S1			42
THE ACQUISITION, BACKGROUND AND REASONS FOR THE EXCHANGE OFFER			43
The Proposed Acquisition; Plans and Proposals			43
Background of the Exchange Offer			45
Reasons for the Exchange Offer
THE EXCHANGE OFFER			57
Overview			57
Expiration Time of the Exchange Offer			58
Extension, Termination and Amendment			58
Acceptance for Exchange and Exchange of S1 Shares; Delivery of Exchange Offer Consideration			60
Cash In Lieu of Fractional ACI Shares			61
Elections and Proration			61
Consequences of Tendering with No Election			62
Procedure for Tendering			62
Withdrawal Rights			65
Announcement of Results of the Exchange Offer			65
Ownership of ACI After the Exchange Offer			65
Certain Material Federal Income Tax Consequences			65
Purpose and Structure of the Exchange Offer			69
Second-Step Merger			69
Appraisal/Dissenters’ Rights			69
Plans for S1			70
Effect of the Exchange Offer on the Market for S1 Shares; NASDAQ Listing; Registration Under the Securities Exchange Act of 1934; Margin Regulations			71
Conditions of the Exchange Offer			72
Dividends and Distributions			75
Source and Amount of Funds			76
Interest; Letter of Credit Fees; Unused Commitment Fees			76
Certain Legal Matters; Regulatory Approvals			82
Certain Relationships With S1 and Interests of ACI in the Exchange Offer			84
Fees and Expenses			84
Accounting Treatment			85
DESCRIPTION OF ACI CAPITAL STOCK			87
COMPARISON OF STOCKHOLDERS’ RIGHTS			89
Authorized Capital			89
Number of Directors			89

			Page
Structure of Board of Directors; Term of Directors			89
Removal of Directors			89
Vacancies on the Board of Directors			89
Special Meetings of Stockholders			89
Stockholder Proposals			90
Stockholder Nominations			91
Amendment of Certificate of Incorporation			94
Amendment of By-Laws			94
Limitations on Director Liability			94
Dividends			94
Stockholder Rights Plan			94
Restrictions on Business Combination			94
UNAUDITED CONDENSED COMBINED PRO FORMA FINANCIAL INFORMATION			95
FORWARD-LOOKING STATEMENTS			106
LEGAL MATTERS			106
EXPERTS			106
SOLICITATION OF PROXIES			107
ADDITIONAL NOTE REGARDING THE EXCHANGE OFFER			107
WHERE YOU CAN FIND MORE INFORMATION			108
NOTE ON S1 INFORMATION			110
APPENDIX A DIRECTORS AND EXECUTIVE OFFICERS OF ACI			A-1
APPENDIX B DIRECTORS AND EXECUTIVE OFFICERS OF OFFEROR			B-1
APPENDIX C STOCK TRANSACTIONS IN THE PAST 60 DAYS			C-1
EX-5.1
EX-23.1
EX-23.2
EX-99.1
EX-99.2
EX-99.3
EX-99.4

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transaction. Based on the $35.70 closing trading price per ACI Share on July 25, 2011, the last trading day prior to the Original ACI Merger Proposal, the relative value of the cash-stock consideration reflected by the Original ACI Merger Proposal as of such date consisted of $5.70 in cash and $3.80 in ACI Shares per S1 Share (or an implied exchange ratio of 0.1064 shares), assuming full proration, or an aggregate value of $9.50 per S1 Share. On August 2, 2011, S1 announced that the S1 Board had rejected the Original ACI Merger Proposal.

     On August 25, 2011, ACI publicly announced the Enhanced ACI Merger Proposal, increasing the cash consideration payable under the Original ACI Merger Proposal by $0.50 per share, assuming full proration (which, based on the closing trading prices as of July 26, 2011, the date of the Original ACI Merger Proposal, would result in a blended value, assuming full proration, of $10.00 per S1 Share).

     Based on the $30.49 closing trading price per ACI Share on August 29, 2011, the last trading day prior to this Exchange Offer, the relative value of the Cash-Stock Consideration reflected by this Exchange Offer consisted of $6.20 in cash and $3.24 in ACI Shares per S1 Share as of such date, or an aggregate blended value of $9.44 per S1 Share as of such date, assuming full proration. ACI is making the Exchange Offer directly to S1 stockholders on the terms and conditions set forth in this prospectus/offer to exchange as an alternative to the Enhanced ACI Merger Proposal.

     When it made the Original ACI Merger Proposal to S1, ACI stated that it is prepared to enter into a merger agreement with S1 that includes substantially similar non-price terms and conditions to the Fundtech Merger Agreement and delivered to the S1 Board a merger agreement reflecting such terms and conditions.

     The equity capital markets have been highly volatile since July 26, 2011 and market prices for ACI Shares have fluctuated and will fluctuate, and could be higher or lower than the price of ACI Shares at or after the Expiration Time. Accordingly, S1 stockholders are urged to obtain current trading price information for ACI Shares prior to deciding whether to tender shares pursuant to the Exchange Offer, whether to exercise withdrawal rights as provided herein and, with respect to the election, whether to receive the Cash Consideration or the Stock Consideration or some combination thereof.

     Have you discussed the Exchange Offer with the S1 Board?

     No, we have not, although we would prefer to discuss our proposal with S1. S1 announced on August 2, 2011 that the S1 Board would not discuss our July 26, 2011 proposal with us based on the S1 Board’s determination that pursuing discussions with ACI at this time is not in the best financial or strategic interests of S1 and its stockholders. Because S1 has not begun negotiations with us despite our request to do so, we made this Exchange Offer without discussing it with S1.

     ACI reserves the right to solicit proxies or consents to cause the S1 Board to be reconstituted with director nominees proposed by ACI independently of or in connection with the Exchange Offer. Any such proxy solicitation will be made only pursuant to separate proxy materials in accordance with the rules and regulations of the SEC.

     What is the purpose of the Exchange Offer?

     The Exchange Offer is intended to allow ACI, through Offeror, to acquire all of the issued and outstanding S1 Shares. In connection with consummation of the Exchange Offer, and subject to applicable law, ACI currently expects to replace the existing S1 Board or increase the size of the S1 Board and elect ACI nominees who would in the aggregate constitute a majority of the members of the S1 Board.

     We intend, as promptly as possible after completion of the Exchange Offer, to consummate a Second-Step Merger of S1 with and into Offeror (the “Second-Step Merger”) pursuant to the General Corporation Law of the State of Delaware, as amended (the “DGCL”). The purpose of the Second-Step Merger is for ACI to acquire all outstanding S1 Shares that are not acquired in the Exchange Offer. In this Second-Step Merger, each remaining S1 Share (other than shares held in treasury by S1 and other than shares held by S1 stockholders who properly exercise applicable dissenters’ rights under Delaware law) would be cancelled and exchanged for the Proration Amount of Cash and Stock Consideration. After this Second-Step Merger, ACI would own all of the issued and outstanding S1 Shares. Please see the sections of this prospectus/offer to exchange titled “The Exchange Offer—Purpose and Structure of the Exchange Offer”; “The Exchange Offer—Second-Step Merger”; and “The Exchange Offer—Plans for S1.”

     Why is the Exchange Offer superior to the Proposed Fundtech Merger?

     ACI believes that the Exchange Offer is superior to the Proposed Fundtech Merger notwithstanding the S1 Board’s rejection of the Original ACI Merger Proposal because it provides greater and more certain value than the Proposed Fundtech Merger. Among other things, in the Exchange Offer, 62.0% of S1 Shares would be exchanged for cash. The Proposed Fundtech Merger provides no cash to S1 stockholders. However, 38.0% of the consideration in the Exchange Offer is in the form of ACI Shares, and there necessarily can be no assurance as to its future value. See the section of this prospectus/offer to exchange titled “Risk Factors.” For more details regarding the reasons for

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(1)		Debt (long-term portion) includes long-term capital lease obligations of $1.3 million, $2.4 million, $1.8 million, $1.5 million, $1.0 million, $0.9 million, $1.5 million, and $3.1 million as of June 30, 2011 and 2010, December 31, 2010, 2009, 2008 and 2007, and September 30, 2007 and 2006, respectively, which is included in other noncurrent liabilities in the consolidated balance sheets.

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(2)		ACI’s revolving credit facility has a maturity date of September 29, 2011; therefore, it has moved to current from long-term. The commitment letter from Wells Fargo Securities and Wells Fargo Bank described in the section of this prospectus/offer to exchange titled “The Exchange Offer—Source and Amount of Funds” would refinance ACI’s existing indebtedness in addition to provide cash to be used (in addition to ACI’s cash on hand) to finance the cash portion of the Exchange Offer.
(3)		On February 27, 2007, ACI’s Board of Directors approved a change in ACI’s fiscal year from a September 30 fiscal year-end to a December 31 fiscal year-end, effective as of January 1, 2008 for the year ended December 31, 2008.

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(1)		Revenue from State Farm.
(2)		Cash used in financing activities included the repurchase of common stock of $9.6 million in 2009, $25.1 million in 2008, $51.0 million in 2007 and $55.8 million in 2006 pursuant to authorized stock repurchase programs.
(3)		S1’s 2010 selected financial data reflects, as of their respective dates of acquisition, S1’s purchase of PM Systems Corporation for approximately $29.2 million, net of cash acquired, in March 2010 and certain assets from a reseller in Latin America for approximately $1.9 million, net of cash acquired, in August 2010.
(4)		In 2004, S1 acquired Mosaic Software Holdings Limited and S1 paid an additional acquisition cost of $14.0 million as earn-out consideration in 2006. Discontinued operations included S1’s Risk and Compliance business sold in 2006 for approximately $32.6 million.
(5)		Working capital includes deferred revenue of $50.0 million and $38.0 million as of June 30, 2011 and December 31, 2010, respectively.
(6)		Working capital includes deferred revenue of $36.8 million and $26.8 million as of June 30, 2010 and December 31, 2009, respectively.

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Risk Factors Relating to ACI’s Businesses

     You should read and consider other risk factors specific to ACI’s businesses that will also affect ACI after the acquisition contemplated by this prospectus/offer to exchange, described in Part I, Item 1A of the ACI 10-K and other documents that have been filed by ACI with the SEC and which are incorporated by reference into this prospectus/offer to exchange. See the section of this prospectus/offer to exchange titled “Where You Can Find More Information.”

anti-assignment, change of control or similar clause. If this happens, ACI may have to seek to replace that agreement with a new agreement. ACI cannot assure you that it will be able to replace a terminated agreement on comparable terms or at all. Depending on the importance of a terminated agreement to S1’s business, failure to replace that agreement on similar terms or at all may increase the costs to ACI of operating S1’s business or prevent ACI from operating part or all of S1’s business.

Future results of the combined company may differ materially from the Selected Unaudited Condensed Consolidated Pro Forma Financial Information of ACI and S1 presented in this prospectus/offer to exchange.

     The future results of ACI following the consummation of the Exchange Offer may be materially different from those shown in the Selected Unaudited Condensed Consolidated Pro Forma Financial Information presented in this prospectus/offer to exchange, which show only a combination of ACI’s and S1’s historical results after giving effect to the Exchange Offer. ACI has estimated that it will record approximately $25.8 million in transaction expenses, as described in the notes to the Selected Unaudited Condensed Consolidated Pro Forma Financial Information included in this prospectus/offer to exchange. In addition, the final amount of any charges relating to acquisition accounting adjustments that ACI may be required to record will not be known until following the consummation of Exchange Offer and Second-Step Merger. These and other expenses and charges may be higher or lower than estimated.

Our business, which depends heavily on revenue from customers in the banking and insurance industries and other financial services firms, may be materially adversely impacted by volatile U.S. and global market and economic conditions, which could adversely affect the value of ACI Shares received as part of the Exchange Offer.

     For the foreseeable future, we expect to continue to derive most of our revenue from products and services we provide to the banking and insurance industries and other financial services firms and retailers. Given the concentration of our business activities in financial industries, we may be particularly exposed to economic downturns in those industries. U.S. and global market and economic conditions have been disrupted and volatile over the past several years. General business and economic conditions that could affect us and our customers include fluctuations in debt and equity capital markets, liquidity of the global financial markets, the availability and cost of credit, investor and consumer confidence, and the strength of the economies in which our customers operate. A poor economic environment could result in significant decreases in demand for our products and services, including the delay or cancellation of current or anticipated projects, and adversely affect our operating results. In addition to mergers and acquisitions in the banking industry, we have seen an increased level of bank closures and government supervised consolidation transactions. Our existing customers may be acquired by or merged into other financial institutions that have their own financial software solutions, be closed by regulators, or decide to terminate their relationships with us for other reasons. As a result, our sales could decline if an existing customer is merged with or acquired by another company or closed. Additionally, our investment portfolio is generally subject to credit, market, liquidity and interest rate risks and the value and liquidity of our investments may be adversely impacted by U.S. and global market and economic conditions including bank closures.

THE COMPANIES

ACI

     ACI is a Delaware corporation with its principal executive offices located at 120 Broadway, Suite 3350, New York, New York 10271. The telephone number of ACI is (646) 348-6700. ACI develops, markets, installs and supports a broad line of software products and services primarily focused on facilitating electronic payments. In addition to its own products, ACI distributes, or acts as a sales agent for, software developed by third parties. These products and services are used principally by financial institutions, retailers and electronic payment processors, both in domestic and international markets. Most of ACI’s products are sold and supported through distribution networks covering three geographic regions — the Americas, Europe/Middle East/Africa and Asia/Pacific. As of June 30, 2011, ACI had total stockholders’ equity of approximately $280 million and total assets of approximately $614 million. ACI Shares are listed on the NASDAQ Global Select Market under the ticker symbol “ACIW” and, as of August 29, 2011, the last practicable date prior to the filing of this prospectus/offer to exchange, ACI had a market capitalization of approximately $1,067.2 million. As of December 31, 2010, ACI had a total of approximately 2,134 employees, of whom 1,124 were in the Americas reportable segment, 591 were in the Europe/Middle East/Africa reportable segment and 419 were in the Asia/Pacific reportable segment.

     As of the date of the filing of this prospectus/offer to exchange with the SEC, ACI was the beneficial owner of 1,107,000 S1 Shares, or 2.0% of the amount outstanding.

Offeror

     Offeror, a Delaware limited liability company, is a wholly-owned subsidiary of ACI. Offeror is newly formed, and was organized for the purpose of making the Exchange Offer and consummating the Second-Step Merger. Offeror has engaged in no business activities to date and it has no material assets or liabilities of any kind, other than those incident to its formation and those incurred in connection with the Exchange Offer and the Second-Step Merger.

S1

     S1 is a leading global provider of payments and financial services software solutions. S1 offers payments solutions for ATM and retail point-of-sale driving, card management, and merchant acquiring, as well as financial services solutions for consumer, small business and corporate online banking, trade finance, mobile banking, voice banking, branch and call center banking. S1 sells its solutions primarily to banks, credit unions, retailers and transaction processors and also provides software, custom software development, hosting and other services to State Farm Mutual Automobile Insurance Company, a relationship that will conclude by the end of 2011. Founded in 1996, S1 started the world’s first Internet bank, Security First Network Bank. In 1998, S1 sold the banking operations and focused on software development, implementation and support services. For several years, S1’s core business was primarily providing Internet banking and insurance applications. Then, through a series of strategic acquisitions and product development initiatives, S1 expanded its solution set to include applications that deliver financial services across multiple channels and provide payments and card management functionality.

     S1 Shares are listed on the NASDAQ under the ticker symbol “SONE.” S1’s principal executive offices are located at 705 Westech Drive, Norcross, Georgia 30092 and its telephone number is (404) 923-3500.

THE ACQUISITION, BACKGROUND AND REASONS FOR THE EXCHANGE OFFER

The Proposed Acquisition; Plans and Proposals

     In its effort to consummate the acquisition of S1, ACI is pursuing the following alternative transactions:

     (1) the Enhanced ACI Merger Proposal (the S1 Board rejected the Original ACI Merger Proposal on or about August 2, 2011); and

     (2) the Exchange Offer.

The Enhanced ACI Merger Proposal and the Exchange Offer are alternative methods for ACI to acquire S1. Ultimately, only one of these transactions can be pursued to completion. ACI intends to seek to acquire S1 by whichever method ACI determines is most likely to be completed.

     On July 26, 2011, ACI publicly announced the Original ACI Merger Proposal to combine the businesses of ACI and S1 through a merger transaction in which ACI would acquire all of the issued and outstanding S1 Shares in a cash and stock transaction. Based on the $35.70 closing trading price per ACI Share on July 25, 2011, the last trading day prior to the Original ACI Merger Proposal, the relative value of the Cash-Stock Consideration reflected by the Original ACI Merger Proposal as of such date consisted of $5.70 in cash and $3.80 in ACI Shares per S1 Share (or an implied exchange ratio of 0.1064 shares), assuming full proration, or an aggregate value of $9.50 per S1 Share. On August 2, 2011, S1 announced that the S1 Board had rejected the Original ACI Merger Proposal, stating:

“S1 Corporation (Nasdaq: SONE) announced today that its Board of Directors, after thorough consideration and consultation with its legal and financial advisors, has rejected ACI Worldwide, Inc.’s (“ACI”) previously announced proposal to acquire S1. The Board unanimously concluded that pursuing discussions with ACI at this time is not in the best financial or strategic interests of S1 and its stockholders. In doing so, the Board affirmed its commitment to S1’s pending business combination with Fundtech.

‘The S1 Board gave careful consideration to each of the proposed terms and conditions of ACI’s proposal. In the end, the Board determined that ACI’s proposal is not in the best interests of S1 and its stockholders. We believe that continuing to execute on our long-term business plan, which includes the business combination with Fundtech, will best help us maximize stockholder value and achieve our strategic goals,’ stated John W. Spiegel, Chairman of the Board of Directors of S1.”

     On August 25, 2011, ACI publicly announced the Enhanced ACI Merger Proposal, increasing the cash consideration payable under the Original ACI Merger Proposal by $0.50 per S1 Share, assuming full proration (which, based on the closing trading prices as of July 26, 2011, the date of the Original ACI Merger Proposal, would result in a blended value, assuming full proration, of $10.00 per S1 Share). Based on the closing sales price for ACI Shares on August 29, 2011, the last trading day prior to the commencement of the Exchange Offer, the blended value of the Cash-Stock Consideration as of the close of trading on August 29, 2011 was $9.44 per S1 Share, assuming full proration.

     On August 25, 2011, ACI filed a proxy statement in connection with its solicitation of proxies against the adoption of Fundtech Merger Proposals and a vote against such proposals brought before any S1 Special Stockholder Meeting as discussed in more detail in such proxy statement.

     ACI would prefer to acquire S1 in a merger transaction of the type contemplated by the Enhanced ACI Merger Proposal. However, in light of the S1 Board’s rejection of the Original ACI Merger Proposal, ACI is making the Exchange Offer directly to S1 stockholders on the terms and conditions set forth in this prospectus/offer to exchange as an alternative to the Enhanced ACI Merger Proposal. The amount of cash and the number of ACI Shares offered in this Exchange Offer are the same as in the Enhanced ACI Merger Proposal.

     S1 has the right to terminate the Fundtech Merger Agreement and enter into a merger agreement with a third party such as ACI in certain events, including in the event that the S1 Board determined that such third party’s proposed transaction constitutes a “Parent Superior Proposal” under the Fundtech Merger Agreement. As discussed in “Reasons for the Exchange Offer” below, ACI believes that the Enhanced ACI Merger Proposal is superior financially and otherwise to the Fundtech Merger Proposal. However, in order for S1 to terminate the Fundtech Merger Agreement, the S1 Board must determine that the Enhanced ACI Merger Proposal, or the Exchange Offer, “constitutes or would reasonably be expected to result in a Parent Superior Proposal,” and on or about August 2,

2011, the S1 Board rejected the Original ACI Merger Proposal and reaffirmed S1’s commitment to the Proposed Fundtech Merger. S1 also may terminate the Fundtech Merger Agreement if S1 stockholders vote against the approval of the issuance of S1 Shares in the Proposed Fundtech Merger and in certain other events. ACI intends, if applicable, to vote any S1 Shares beneficially owned by it, including S1 Shares purchased in the Exchange Offer from holders of record as of the record date of the S1 Special Stockholder Meeting if such meeting is delayed or adjourned, against the issuance of S1 shares in the Proposed Fundtech Merger and is soliciting proxies from S1 stockholders voting against such issuance.

     Termination of the Fundtech Merger Agreement is one of the conditions to the Exchange Offer. Whether or not ACI will waive this condition will depend on future facts which cannot presently be ascertained, including how many S1 Shares are tendered pursuant to the Exchange Offer and actions taken by S1, the S1 Board and S1 stockholders. If the Fundtech Merger Agreement were terminated, S1 may be required to pay Fundtech a $14.6 million break-up fee. The payment of such fee is permitted by the Exchange Offer, was contemplated in the Enhanced ACI Merger Proposal and will not be considered by ACI in deciding whether the conditions to the Exchange Offer have been satisfied. See “Conditions to the Exchange Offer.”

     In the event that Offeror accepts S1 Shares for exchange in the Exchange Offer, ACI, through Offeror, intends to acquire any additional outstanding S1 Shares pursuant to the Second-Step Merger, although ACI, through Offeror, also reserves the right, subject to applicable law, to acquire S1 Shares pursuant to other means, including open market purchases and privately negotiated transactions. If Offeror accepts S1 Shares for exchange and, pursuant to the Exchange Offer or otherwise, owns 90% or more of the outstanding S1 Shares, the Second-Step Merger can be effected as a “short form” merger under Delaware law without the consent of any stockholder (other than ACI) and without the approval of the S1 Board. However, if Offeror does not acquire at least 90% of the outstanding S1 Shares in the Exchange Offer or otherwise, then both S1 Board approval and S1 stockholder approval would be required to effect the Second-Step Merger.

     If the Exchange Offer is completed and Offeror acquires a majority of the outstanding S1 Common Stock, subject to applicable law, ACI currently expects to seek to replace the existing S1 Board or increase the size of the S1 Board and elect ACI nominees who would in the aggregate constitute a majority of the members of the S1 Board. See Appendix A to this prospectus/offer exchange for information as to the individuals, all of whom are currently directors or officers of ACI, that ACI currently expects it would propose to elect to the S1 Board. S1’s certificate of incorporation provides for staggered director terms. Under Delaware law, the members of the S1 Board cannot be removed during their respective terms in office other than for cause. However, S1’s certificate of incorporation also permits stockholders to act by written consent in lieu of a meeting, and ACI believes that it could act by written consent to change the composition of the S1 Board. ACI reserves the right, subject to applicable law, to commence a consent solicitation or take other action prior to or after the Expiration Time of the Exchange Offer to seek to change the composition of the S1 Board. ACI’s director nominees pursuant to such consent solicitation, if it occurs, may include persons other than those identified on Appendix A. Any such consent solicitation will be made only pursuant to separate consent solicitation materials filed with and in accordance with the requirements of the rules and regulations of the SEC.

     Under Section 203 of the DGCL, ACI may not effect the Second-Step Merger for a period of three years following the acquisition of S1 Shares in the Exchange Offer unless (1) ACI obtains the approval of the S1 Board prior to obtaining beneficial ownership of more than 15% of the S1 Shares, (2) ACI acquires beneficial ownership of at least 85% of the outstanding S1 Shares in the Exchange Offer or another transaction in which it acquires greater than 15% ownership of S1, or (3) if either the conditions set forth in clause (1) or (2) is not satisfied, the Second-Step Merger is approved by the S1 Board and the holders of at least two-thirds of the outstanding S1 Shares not owned by ACI. The completion of the Exchange Offer is subject to the Delaware 203 Condition, which means either that (1) or (2) must apply. Whether or not ACI will waive this condition will depend on future facts which cannot presently be ascertained, including how many S1 Shares are tendered pursuant to the Exchange Offer and actions taken by S1 or the S1 Board.

     For more details relating to the structure of the Exchange Offer, please see the section of this prospectus/offer to exchange titled “The Exchange Offer.”

Background of the Exchange Offer

     As part of the ongoing evaluation of its businesses, ACI regularly considers strategic acquisitions, capital investments, divestitures and other possible transactions. In connection with such strategic evaluation, ACI has in the past considered a potential business combination transaction involving S1 and in connection therewith engaged in discussions with representatives of S1 over an approximately one-year period beginning in the Summer of 2010.

     On August 30, 2010, Philip G. Heasley, ACI’s Chief Executive Officer, met in Atlanta, Georgia, with Johann Dreyer, S1’s Chief Executive Officer. During that meeting, Mr. Heasley expressed an interest in pursuing a possible acquisition of S1 by ACI.

     On September 30, 2010, members of ACI’s senior management met in Atlanta, Georgia with members of S1’s senior management to discuss a possible acquisition of S1 by ACI. In that meeting, the representatives of ACI indicated a possible price range of $7.50 to $8.00 per S1 Share. The closing sales price for S1 Shares as reported on the NASDAQ Market was $5.25 per share on September 29, 2010, the last trading day prior to that meeting. At the meeting, Mr. Dreyer indicated that he did not believe that it was opportune timing for S1 to be sold, but S1 might consider an enhanced proposal.

     On October 6, 2010, representatives of S1 and ACI had a follow-up conversation in which the representatives of S1 informed the representatives of ACI that, after reviewing the matter with the S1 Board, S1 was not for sale and the S1 Board did not desire to initiate a sale process. They also mentioned that they believed that the price range that ACI had indicated was too low, but indicated that the S1 Board might be willing to consider a transaction at an increased valuation. ACI interpreted that communication as meaning that S1 would consider a transaction at a higher price other than the $7.50-$8.00 per share range that ACI had indicated, although there can be no assurance that this was intended. In the October 6, 2010 call, the representatives of S1 also said that the S1 Board acknowledged the rationale for a possible combination of S1 and ACI, but indicated that S1 would be willing to continue discussions only if the parties signed a standstill agreement.

     On October 22, 2010, S1 and ACI signed an agreement that restricted ACI’s ability to acquire S1 Shares or make any tender offer or other proposal to acquire S1. These restrictions expired prior to July 26, 2011. During the standstill period, ACI did not buy any S1 Shares and made proposals to acquire S1 confidentially.

     On October 25, 2010, representatives of ACI’s and S1’s managements and financial advisors met in Atlanta, Georgia to discuss the S1 business and a possible transaction. From time to time thereafter, certain of S1’s senior managers, representatives of S1’s financial advisor and S1’s counsel held additional discussions with members of ACI’s senior management team and legal and financial advisors concerning a possible transaction.

     On November 19, 2010, ACI submitted a written proposal to S1 to acquire S1 in an all-cash transaction at a price of $8.40 per S1 Share, subject to confirmatory due diligence. ACI included a letter from a major financial institution stating that such institution was highly confident that ACI could raise the funds necessary to acquire S1 in an all-cash transaction at $8.40 per share. In the November 19, 2010 proposal, ACI noted, among other things, “[w]e believe our proposal constitutes an extremely attractive opportunity for your stockholders. Our price represents a premium of 38% over the current market price of S1’s common stock and a premium of 42% over the average market price over the past year.” After ACI submitted the proposal letter, S1 representatives raised concerns about ACI’s ability to finance an all-cash acquisition of S1 and regulatory considerations. ACI representatives indicated that ACI believed that it could satisfy any such concerns, and undertook to do so.

     On December 9, 2010, Mr. Heasley spoke with Messrs. Dreyer and John W. Spiegel, Chairman of the S1 Board, regarding ACI’s November 19th proposal. The parties also discussed ACI and S1’s overlapping stockholder base and the potential for a mix of stock and cash consideration in an ACI-S1 transaction. On December 20, 2010, ACI delivered a draft merger agreement to S1. The draft merger agreement contemplated the payment of the purchase price in cash or stock, as elected by S1 stockholders.

     From time to time between December 2010 and February 2011, representatives of ACI’s management and ACI’s legal and financial advisors held additional discussions with representatives of S1’s management and S1’s legal and financial advisors concerning a possible transaction. On January 13, 2011, ACI sent a follow-up letter to

S1 in an effort to progress the dialogue between the parties and to commence due diligence. During January 2011, S1’s financial advisor on several times rescheduled a lender due diligence session, which was finally scheduled for March 3, 2011 but cancelled after S1 sent a letter to ACI on February 18, 2011 stating among other things that S1 was terminating discussions with ACI as the S1 Board had “determined that it is in the best interests of S1 and its stockholders to focus our efforts on executing our long-term business plan.”

     On March 10, 2011, S1 published its 2010 earnings release and provided public guidance with respect to its 2011 outlook. In late March 2011, Mr. Heasley initiated contact with S1 in an effort to continue discussion regarding a possible transaction. On April 5, 2011, Mr. Heasley met in person with Messrs. Dreyer and Spiegel in Atlanta, Georgia. On April 12, 2011, ACI submitted an acquisition proposal (including a revised draft of a definitive merger agreement) at a price of $8.40 per S1 Share, 55% of which was to be paid in cash and 45% in ACI Shares. In its proposal, ACI noted, among other things, “[t]his proposal represents a premium of 26.1% over the current market price of S1’s common stock and a premium of 37.4% over the average market price over the past year. We believe that this price is at a level at which your stockholders would enthusiastically support such a transaction.”

     On April 15, 2011, representatives of ACI’s financial advisor held a discussion with representatives of S1’s financial advisor regarding ACI’s proposal. The financial advisors had additional contacts from time to time concerning the proposal between April 15, 2011 and June 14, 2011.

     On June 14, 2011, Mr. Heasley spoke with Messrs. Dreyer and Spiegel regarding ACI’s proposal. During the call, Mr. Spiegel informed Mr. Heasley that S1 was not interested in pursuing a possible transaction with ACI. No mention was made that S1 was simultaneously pursuing discussions with Fundtech relating to a possible merger transaction. Later that day, Mr. Heasley sent a follow-up letter to Mr. Spiegel requesting a response from the S1 Board regarding ACI’s proposed valuation and other key terms. The June 14, 2011 letter, in relevant part, is as follows:

“June 14, 2011

Mr. John W. Spiegel
Chairman of the Board of Directors
S1 Corporation
705 Westech Drive
Norcross, Georgia 30092

Dear John,

I appreciated your feedback during our call this morning. I was surprised by your Board’s lack of response to our April 12th proposal.

ACI and our advisors have complied with all of the process requirements that S1 management and your advisors have communicated to us since last Fall. First, our financing advisors, Goldman Sachs and Wells Fargo, have had multiple interactions with S1 management and your advisor providing you with certainty of the financial structure we proposed. Second, our legal advisor, Jones Day, has had several conversations with your external counsel to address any regulatory concerns around the proposed transaction. Also, Jones Day submitted on December 20, 2010, a fair and balanced merger agreement and a revised version on April 12, 2011, to which we have still not received any feedback.

We have studied the regulatory backdrop applicable to the proposed transaction. As reflected in the April 12th merger agreement, we believe the regulatory review process will not impact the certainty of closing and we have outlined measures in the agreement that demonstrate our confidence in this view.

To date, your Board has not provided any response to our proposed valuation or other key terms. We would have liked to have had a discussion on value, but are now left to determine valuation based on publicly available information. With the nine-month standstill period expiring on July 22nd, we still believe it would be in the best interests of S1 and your Board to engage with ACI to maximize value for S1’s shareholders.

The combination of ACI and S1 would create a leading global player in the enterprise payments software industry. As I have indicated, the combination of our companies would not only benefit your shareholders, but would also offer more and better options to customers within our marketplace. We sincerely hope that we will move forward in a negotiated transaction which can be presented to your stockholders as the joint effort of ACI and S1 Boards of Directors and management teams.

This opportunity has the highest priority for us and we are committed to work with S1 and your Board in any way we can to expeditiously move this forward.

cc: Mr. Johann Dreyer, Chief Executive Officer, S1 Corporation”

     On June 27, 2011, S1 and Fundtech announced that they had entered into the Fundtech Merger Agreement.

     On July 26, 2011, ACI delivered a proposal letter containing the Original ACI Merger Proposal to the S1 Board and issued a press release announcing the Original ACI Merger Proposal. The letter read as follows:

“July 26, 2011

Board of Directors
S1 Corporation
705 Westech Drive
Norcross, Georgia 30092
Attn: Mr. John W. Spiegel, Chairman of the Board

Gentlemen:

We are pleased to submit the following proposal by which ACI Worldwide and S1 Corporation would combine to create a leading global enterprise payments company. We propose to acquire 100% of the issued and outstanding common stock of S1 in a cash and stock transaction valued at $9.50 per share. This equates to a 33% premium to S1’s closing market price on July 25, 2011, a 32% premium to S1’s 90-day volume weighted average price and a 23% premium to S1’s 52-week high. Our proposal is being made pursuant to and in accordance with the superior offer provisions you provided for in your June 26, 2011 merger agreement with Fundtech.

Given the overlapping shareholder base of our companies, we believe that a cash and stock transaction is ideal for all stakeholders, as it provides a mix of immediate value, tax efficiency and the ability to benefit from significant synergies. Accordingly, the form of consideration in our proposal consists of 40% in ACI stock and 60% in cash. In addition, our proposal includes a cash election feature, subject to proration, designed to provide your shareholders with the optimal consideration of cash and/or stock for their individual circumstances and preferences. Upon completion of our proposed transaction and based on the most recent closing price of ACI’s common stock, S1 shareholders would own approximately 15% of the combined company on a fully diluted basis.

We believe the combination of ACI and S1 provides specific tangible benefits to the combined shareholders, including, among others:

• Combination of complementary products and expanded customer bases, providing a rich set of capabilities and a broad portfolio of products to serve customers across the entire electronic payments spectrum;

• The creation of an approximate $100 million in revenue hosting business serving our collective customer base with enhanced margins due to the consolidation of fixed infrastructure;

• Expanded presence in high-growth international markets and additional capabilities with respect to ACI’s retailer payments and online banking solutions;

• Substantial synergy opportunities by leveraging ACI’s established global cost structure, eliminating redundant operating expenses and consolidating our on-demand operations and facilities; and

• Strong financial profile with full year earnings accretion in 2012.

We believe that our premium stock and cash proposal is both financially and strategically superior to your proposed transaction with Fundtech. Our proposal offers substantially greater current financial value to S1 shareholders in the form of a meaningful premium to the current stock price and a clearer, more expedient path to value creation over the long-term through the realization of significant synergies, with less risk and uncertainty than the Fundtech transaction. Additionally, our proposed combination creates a more diverse, long-term shareholder base for the pro forma company.

Our proposal contemplates that, following the completion of the transaction, S1 shareholders would have a meaningful ownership stake in ACI, which has:

• Produced a shareholder return of approximately 91% over the past three years, significantly outperforming the relevant peer group;

• Increased 60-month backlog to $1.6 billion in 2010, up $350 million since 2006;

• Driven monthly recurring revenue to 68% in 2010, up nearly 29% since 2007; and

• Increased Adjusted EBITDA margin to 21% in 2010, from 7% in 2007.

Not only have we executed our historical business plan, as evidenced by our strong second quarter earnings, we have raised our 2011 guidance and are firmly committed to achieving our five-year strategy.

Our proposal includes committed financing from Wells Fargo Bank for the cash portion of the transaction. As such, the proposed transaction is not subject to any financing condition. In addition, we have completed a review of applicable regulatory requirements and, while we do not expect any issues to delay closing, our merger agreement contains appropriate undertakings by us to assure HSR clearance.

Our proposal is subject to the negotiation of a mutually acceptable definitive merger agreement, a draft of which we are including as part of our proposal. Consummation of the transaction is subject to satisfaction of customary closing conditions, including expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act. You will see that our draft is the same as the Fundtech Merger Agreement except for changes required in order to effect our transaction. We are prepared to promptly conclude our confirmatory due diligence and to give you and your representatives immediate due diligence access to us.

We believe that our proposal represents a Parent Superior Offer that clearly meets the standards set forth in Section 6.7(a) of your Fundtech Merger Agreement as it is more favorable to S1 shareholders from a financial point of view than the Fundtech transaction, and it is likely to be completed, taking into account all financial, regulatory, legal and other aspects of our proposal. Accordingly, we believe that you must, consistent with the Fundtech Merger Agreement, provide us with confidential information and participate in discussions and negotiations with us to finalize a transaction.

We stand ready and willing to promptly engage with S1 on this transaction, so that together we can effect a transaction that benefits both companies’ shareholders. That said, we are committed to making this transaction a reality.

Our Board of Directors has unanimously approved the submission of this proposal. We and our financial and legal advisors are prepared to move forward immediately with you and your advisors to finalize a mutually beneficial agreement, and make the combination of S1 and ACI a reality, for the benefit of both companies’ shareholders.

We look forward to hearing from you.

Enclosures”

     On July 27, 2011, ACI filed a Notification and Report Form with the FTC and Antitrust Department under the HSR Act relating to the Original ACI Merger Proposal.

     On August 2, 2011, S1 announced that the S1 Board had rejected the Original ACI Merger Proposal based on the S1 Board’s determination that pursuing discussions with ACI at this time “is not in the best financial or strategic interests of S1 and its stockholders.” According to S1’s August 2, 2011 press release, Mr. Spiegel said:

“The S1 Board gave careful consideration to each of the proposed terms and conditions of ACI’s proposal. In the end, the Board determined that ACI’s proposal is not in the best interests of S1 and its stockholders. We believe that continuing to execute on our long-term business plan, which includes the business combination with Fundtech, will best help us maximize stockholder value and achieve our strategic goals.”

     On August 11, 2011, S1 announced that it had set August 18, 2011 as the record date and September 22, 2011 as the date of the S1 Special Stockholder Meeting. On August 22, 2011, S1 filed its definitive proxy statement with the SEC and reported that it had commenced mailing its proxy statement to S1 stockholders on or about August 22, 2011.

     On August 25, 2011, ACI delivered a proposal letter to S1’s Board containing the Enhanced ACI Merger Proposal, increasing the cash consideration by $0.50 per S1 Share, assuming full proration, and issued a press release announcing the Enhanced ACI Merger Proposal. The letter read as follows:

“August 25, 2011

PERSONAL AND CONFIDENTIAL
ELECTRONIC DELIVERY

John W. Spiegel
Chairman of the Board of Directors
S1 Corporation
705 Westech Drive
Norcross, Georgia 30092

Dear John:

We remain committed to acquiring S1 Corporation and are pleased to inform you that we have enhanced our proposal in order to provide S1 shareholders with additional value certainty for their investment. Given the recent significant market volatility, ACI Worldwide, Inc. has increased its cash and stock proposal from $5.70 per share plus 0.1064 ACI shares to $6.20 per share, plus 0.1064 ACI shares, assuming full proration.

We are confident that your shareholders will find our enhanced proposal to be superior to the Fundtech Ltd. transaction, and we stand ready and willing to promptly engage with S1 to consummate a transaction that benefits both companies’ shareholders. Based on the closing price of ACI stock on July 25, 2011, the day prior to our initial proposal, our enhanced proposal provides a per share consideration of $10.00 to each S1 shareholder. Based on the closing price of ACI stock on August 24, 2011, our enhanced proposal provides a per share consideration of $9.29 to each S1 shareholder. ACI’s enhanced proposal also equates to a:

• 30% premium to S1’s unaffected closing market price on July 25, 2011;

• 29% premium to the volume weighted average price of S1 shares over the previous 90 days prior to July 25, 2011; and

• 20% premium to the 52-week high of S1 shares, for the 52-week period ending July 25, 2011.

When evaluating our enhanced proposal, we strongly encourage you to consider at what price levels S1 would be trading absent the ACI proposal. Since we made our proposal on July 26, 2011, the NASDAQ Index has declined by 13% while S1’s stock price, affected by the value of the ACI proposal, has generally avoided the declines experienced in the overall market. Furthermore, we believe that your shareholders know that, had ACI not made its proposal, S1’s share price would have been affected by the overall decline in stock market valuations. We also believe that the S1 shareholder reaction to our proposal, despite the significant ensuing market volatility, underscores its strength.

Your August 22, 2011, shareholder letter questioned whether we had the financing for the cash portion of our merger proposal as well as our commitment to obtain clearance under the Hart-Scott-Rodino (HSR) Act. To resolve these issues, we have a fully executed commitment letter from Wells Fargo Bank, N.A. sufficient to fund the cash required by our proposal and to finance our ongoing operations, and we would be pleased to provide a copy of such commitment letter upon request. In addition, we reiterate that we are willing to provide appropriate assurance of satisfaction of the HSR Act condition, including a divestiture commitment (if required) and substantial break-up compensation. However, it does not withstand scrutiny for S1 to, on the one hand, refuse to engage with us on these issues and, on the other hand, point to these issues as a reason for not engaging in the first place.

As S1 has been unwilling to engage, we are taking the actions we believe necessary to consummate our proposed transaction. We are filing our definitive proxy statement to begin solicitation of votes against the proposed Fundtech transaction and, rest assured, we will take all actions necessary to advance our proposal. We would, however, strongly prefer to begin a direct dialogue with S1’s management and advisors.

We believe that our proposal represents a Parent Superior Offer that clearly meets the standards set forth in Section 6.7(a) of the Fundtech merger agreement as it is more favorable to S1 shareholders from a financial point of view than the Fundtech transaction and it is likely to be completed, taking into account all financial, regulatory, legal and other aspects of our proposal.

We remain convinced of the strategic benefits of this transaction and strongly believe that it is in the best interests of both ACI’s and S1’s shareholders. We look forward to your prompt reply.

cc: Johann Dreyer, Chief Executive Officer, S1 Corporation”

     On August 25, 2011, ACI filed with the SEC and began mailing its proxy statement soliciting votes “AGAINST” the Fundtech Merger Proposals.

     On August 26, 2011, ACI withdrew its initial HSR filing and refiled it on August 29, 2011 in order to permit the Antitrust Division to have additional time to review the filing. The 30-calendar day waiting period recommenced in connection with such refiling so that it now expires, unless terminated earlier or extended at 11:59 p.m., Eastern Time on September 28, 2011.

     On August 29, 2011, a representative of S1 contacted a representative of ACI with respect to the value and certainty of closure of the Enhanced ACI Merger Proposal. There can be no assurance that such inquiry will lead to discussions, or that any such discussions, if conducted in the future, will lead to a transaction. If they were to lead to a transaction, however, the Exchange Offer could be terminated or amended. See “The Exchange Offer—Extension, Termination and Amendment” and “The Exchange Offer—Conditions of the Exchange Offer.”

     On August 29, 2011, ACI filed this prospectus/offer to exchange with the SEC with respect to the Exchange Offer.

Reasons for the Exchange Offer

     While ACI continues to hope that it is possible to reach a consensual transaction with S1, ACI, through Offeror, is making this Exchange Offer directly to S1 stockholders in light of the S1 Board’s rejection of the Original ACI Merger Proposal on August 2, 2011.

Value:

     ACI believes that the Exchange Offer is superior to the Proposed Fundtech Merger notwithstanding the S1 Board’s rejection of the Original ACI Merger Proposal because it provides greater and more certain value than the Proposed Fundtech Merger. Among other things, in the Exchange Offer, 62.0% of S1 Shares would be exchanged for cash. The Proposed Fundtech Merger provides no cash to S1 stockholders.

     In addition, ACI believes that the value per S1 Share in the Exchange Offer is substantially higher than the trading prices for S1 Shares after the announcement of the Proposed Fundtech Merger. On June 24, 2011, the last trading day prior to the announcement of the Fundtech Merger Agreement, the closing sales price of S1 Shares as reported by the NASDAQ Market was $7.54 per share. The closing sales price for S1 Shares declined on June 27, 2011, the day that the Fundtech Merger Agreement was announced, to $7.26 per share. During the period from June 27, 2011 to July 25, 2011, the last trading day prior to the announcement of the Original ACI Merger Proposal, the closing sales price for S1 Shares further declined 1.8% to $7.13 per share, and its volume weighted average closing sales price over this period was $7.25 per share. This compares to an increase of 4.5% for the S&P 500 Index over the same period. ACI believes that the increase in trading prices was primarily attributable to the Original ACI Merger Proposal.

     At the $9.44 per S1 Share value of the Cash-Stock Consideration as of August 29, 2011, assuming full proration, the Exchange Offer represents (1) a 32.4% premium to the closing sales price of S1 Shares on July 25, 2011, the last trading day prior to the public announcement of the Original ACI Merger Proposal, (2) a 30.9% premium to the volume weighted average closing price of S1 Shares over the previous 90 days prior to the announcement of the Original ACI Merger Proposal, and (3) a 21.8% premium to the 52-week high of S1 Shares for the 52-week period ending July 25, 2011.

     S1 stockholders who elect the Cash-Stock Consideration contemplated by the Exchange Offer will be subject to proration. Since the value of ACI Shares fluctuates, the per S1 Share Stock Consideration necessarily could have a value that is different than the per S1 Share Cash Consideration. As a consequence, in the Exchange Offer, S1 stockholders could receive a combination of Cash-Stock Consideration with a value that is different from the value of such consideration on the date of the Exchange Offer, the date of the S1 Special Stockholder Meeting and the date of the consummation of a transaction with ACI.

     The elections of other S1 stockholders would affect whether S1 stockholders received solely the type of consideration they had elected or whether a portion of the consideration S1 stockholders elected were exchanged for another form of consideration as a result of the pro ration procedures contemplated by the Exchange Offer.

     Solely for purposes of illustration, the following table indicates the value of the Stock Consideration and the blended value of the Cash-Stock Consideration based on different assumed prices for ACI Shares.

				Assuming No Proration								Assuming Full Proration
Assumed ACI				Value of				Value of				Value of				Value of				Value of Cash-Stock
Share Price				Stock Consideration				Cash Consideration				Stock Consideration				Cash Consideration				Consideration
$	37.93	(1)		$	10.62			$	10.00			$	4.04			$	6.20			$	10.24
$	35.70	(2)		$	10.00			$	10.00			$	3.80			$	6.20			$	10.00
$	30.49	(3)		$	8.54			$	10.00			$	3.24			$	6.20			$	9.44
$	18.92	(4)		$	5.30			$	10.00			$	2.01			$	6.20			$	8.21

1.		Represents highest sales price for ACI Shares in the 52-Week Period.
2.		Represents closing sales price for ACI Shares on July 25, 2011, the last trading day prior to the announcement of the Original ACI Merger Proposal.
3.		Represents closing sales price for ACI Shares on August 29, 2011, the last trading day prior to the commencement of the Exchange Offer.
4.		Represents the lowest sales price for ACI Shares in the 52-Week Period.

     The equity capital markets have been highly volatile since July 26, 2011 and market prices for ACI Shares and S1 Shares have fluctuated and can be expected to continue to fluctuate. S1 stockholders are urged to obtain current trading price information prior to deciding whether to tender shares pursuant to the Exchange Offer, whether to exercise withdrawal rights as provided herein and, with respect to the election, whether to receive the Cash Consideration or the Stock Consideration or some combination thereof. The premium represented by the Exchange Offer to the Proposed Fundtech Merger may be larger or smaller depending on market prices on any given date and will fluctuate between the date of this prospectus/offer to purchase, the Expiration Time and the date of the consummation of the Exchange Offer.

Strategic Rationale:

     The Exchange Offer provides immediate cash value to S1 stockholders, as well as the opportunity to participate in the value creation in the Exchange Offer through the receipt of ACI Shares. ACI believes that the complementary nature of ACI and S1 creates a compelling opportunity to establish a full-service global leader of financial and payments software with significant scale and financial strength, including as follows:

     • Highly Complementary Product and Customer Bases: Combined, ACI and S1 would provide a rich set of capabilities and a broad portfolio of products to customers across the entire electronic payments spectrum. In particular, ACI believes that the acquisition of S1 would provide breadth and additional capabilities to what ACI does today, including: (1) expand ACI’s retailer business beyond North America; (2) increase ACI’s retail banking payments business down into lower and mid-tier financial institutions; and (3) add function and global reach to ACI’s online business banking offering, including new capabilities around branch banking and trade. The acquisition of S1 would support ACI’s position as a leading provider of the most unified payments solution to serve retail banking, wholesale banking, processors and retailers and would enable its customers to lower their operational costs and improve time-to-market.

     • Enhanced Scale and Global Position: ACI’s, S1’s and Fundtech’s principal competitors are substantially larger companies with greater financial resources than ACI, S1 and Fundtech have. The combined ACI and S1 would have greater scale and critical mass than S1 would have after the Proposed Fundtech Merger. The combined ACI and S1 would have revenue of $683 million and adjusted EBITDA of $123 million for the 12 months ended June 30, 2011, compared to revenue of $379 million and adjusted EBITDA of $43 million for that period for the combined S1 and Fundtech in the Proposed Fundtech Merger. This scale advantage would enable the combined ACI and S1 to more effectively serve its combined global customer base and compete against the very large companies which operate in the electronic payments software business.

     In addition, Fundtech is dependent upon three international financial institutions for a significant portion of its revenue. According to published reports, in fiscal year 2010, Fundtech derived approximately 21% of its total annual revenues from these three international financial institutions. In comparison, ACI’s top 10 customers represented approximately 20% of its total annual revenue in 2010.

     • Significant Synergy Opportunities: ACI expects the combination of ACI and S1 will generate a significant amount of operational efficiencies and cost savings that will drive margin expansion for the acquired S1 business and earnings accretion for the combined company. ACI estimates that the annual pre-tax cost savings related to the Exchange Offer would be more than double the $12 million estimated in the Proposed Fundtech Merger, primarily attributable to elimination of S1’s public company costs and rationalization of duplicate general and administrative functions, sales/marketing functions and costs, occupancy costs, product management and R&D functions. In addition, ACI expects to consolidate the combined company’s hosting data centers and infrastructure. Further, ACI expects the cost savings will improve S1’s margins in line with ACI’s margins for adjusted EBITDA. Assuming that the Exchange Offer is closed in the fourth calendar quarter of this year, ACI anticipates the cost savings would be fully realizable in 2012.

     • Strong Financial Position: ACI would continue to have a strong financial profile driven by a solid balance sheet with substantial liquidity and a recurring revenue model that generates significant free cash flows, allowing for further future investments in the business. In addition, ACI expects the transaction to be accretive to full year earnings in 2012.

     The following metrics provide relevant information with respect to ACI’s recent financial performance, as of July 26, 2011, the date of the Original ACI Merger Proposal:

	•		ACI has produced a stockholder return of approximately 90% over the past three years, significantly outperforming the relevant peer group;
	•		ACI has increased its 60-month backlog to $1.6 billion in 2010, up $350 million since 2006;
	•		ACI has driven monthly recurring revenue to 68% in 2010, up nearly 29% since 2007; and
	•		ACI has increased adjusted EBITDA margin to 21% in 2010, from 7% in 2007.

     This prospectus/offer to exchange includes summary selected unaudited pro forma combined financial information that is intended to provide S1 stockholders with information relating to ACI’s financial results assuming that ACI and S1 had already been combined.

Integration:

     ACI believes that there are substantial risks inherent in mergers of equals, which ACI believes are exacerbated by the fact that S1 is a U.S. company headquartered in Norcross, Georgia, while Fundtech is a company with substantial operations in Israel. While there is integration risk in any substantial business combination transaction, ACI’s proposal would not involve the complexities inherent in combining two businesses whose co-CEOs and other senior executives would be located on different continents, and ACI would have the ability to implement integration plans without being required to consider the potential conflicting interests and disynergies implicit in a “merger of equals” in which, for example, the combined company’s top management is expected to be drawn from two disparate organizations.

     S1’s proxy statement discloses that political, economic and military conditions in Israel and the Middle East could negatively impact the combined S1-Fundtech company. Fundtech is an Israeli company with substantial operations in Israel. According to S1’s proxy statement, (1) any major hostilities involving Israel, acts of terrorism or the interruption or curtailment of trade between Israel and its present trading partners could adversely affect the combined company’s operations, (2) several Arab and Muslim countries restrict or prohibit business with Israeli companies and these restrictions may have an adverse impact on the combined company’s operating results, financial condition or the expansion of the combined company’s business, and (3) such boycott, restrictive laws, policies or practices may preclude the combined company from pursuing certain sales opportunities in the future.

     Closing Conditions:

     The completion of the Proposed Fundtech Merger is subject to, among other conditions, approval of the issuance of stock in the transaction by holders of a majority of S1 Shares voting at a meeting held on the matter, the expiration or termination of the waiting period under the HSR Act, as well as a number of conditions unique to a combination of a U.S. and an Israeli company, including receipt of the consent or approval of Israeli tax authorities, the Investment Center of the Israeli Ministry of Trade & Industry and the Israeli Securities Authority.

     The Exchange Offer is subject to the conditions set forth in “The Exchange Offer—Conditions to the Exchange Offer,” including the Fundtech Merger Agreement Condition, the Delaware 203 Condition, the Minimum Tender Condition and the receipt of customary regulatory approvals, including the expiration or termination of the waiting period under the HSR Act. The Fundtech Merger Agreement Condition and the Delaware 203 Condition could be satisfied by action of the S1 Board. In addition, the Fundtech Merger Agreement Condition could be satisfied if S1 stockholders vote against the issuance of shares to complete the Fundtech Merger.

     As of the date of this prospectus/offer to exchange, S1 has not obtained clearance under the HSR Act. S1 reported in its proxy statement that it refiled its Notification and Report Form under the HSR Act with the Antitrust Division on August 17, 2011, recommencing the 30-calendar day waiting period under the HSR Act with respect to S1’s acquisition of shares of Fundtech in the Proposed Fundtech Merger. S1 also reported that it understands that Clal, Fundtech’s largest shareholder, intends to withdraw and refile its Notification and Report Form after August 19, 2011, the date of S1’s proxy statement, which will restart the 30-calendar day waiting period.

     ACI filed the required Notification and Report Form under the HSR Act with the Antitrust Division and the FTC on July 27, 2011. Thereafter, the Antitrust Division informed ACI that, as between the FTC and the Antitrust Division, the Antitrust Division would review ACI’s filing. ACI withdrew its initial filing on August 26, 2011, and refiled it on August 29, 2011 in order to permit the Antitrust Division to have additional time to review the filing. The 30-calendar day waiting period recommenced in connection with such refiling so that it now expires, unless terminated earlier or extended, at 11:59 p.m., Eastern Time on September 28, 2011. The Antitrust Division may extend its review beyond the 30-calendar day waiting period by requesting additional information and documentary material. In the event of such a request, the waiting period would be extended until 11:59 p.m., Eastern time, on the 30th calendar day after ACI has made a proper response to that request as specified by the HSR Act and the implementing rules.

     The combination with S1 would provide ACI with enhanced scale, breadth and additional capabilities to compete more effectively in the highly competitive payment systems marketplace. If ACI were to acquire S1, the combined company would continue to face intense competition from third-party software vendors, in house solutions, processors, IT service organizations and credit card associations, including from companies which are substantially larger and have substantially greater market shares than the combined company would have. Moreover, the dynamic worldwide nature of the industry means that competitive alternatives can and do regularly emerge. Thus, ACI does not believe the transaction would enable it to obtain market power in, or even a significant share of, any relevant market.

     Nonetheless, the Original ACI Merger Proposal contained provisions designed to provide S1 what ACI believed to be an appropriate measure of assurance that the HSR Act condition would be satisfied, including a $21.5 million fee that would be paid to S1 if that condition were not satisfied and an undertaking to divest assets, subject to certain limitations (which were not specified in the draft merger agreement delivered to S1), and take other actions if necessary to obtain the expiration or termination of the HSR Act waiting period. ACI reiterated this commitment in connection with its delivery of the Enhanced ACI Merger Proposal.

     Based on the foregoing, ACI believes that it will obtain clearance under the HSR Act, although there necessarily can be no assurance with respect thereto.

     Restructuring of S1 for No Premium and No Cash:

     According to S1’s proxy statement, S1 has entered into a transaction to “acquire” Fundtech in which S1 stockholders will receive no premium and no cash for their shares. Although S1 has stated in its proxy statement

that S1 will “acquire” Fundtech, we believe that its analysis is incorrect. We believe that the Proposed Fundtech Merger is in fact a transaction that results in a radical restructuring of the business, ownership and governance of S1, and thereby could be deemed to constitute de facto change in control of S1 for a number of reasons, including (1) changes in S1’s Board and management, including a governance mechanism applicable to key corporate decisions that requires agreement of designees of each of S1 and Fundtech post-transaction (unless approved by a post-transaction Board of Directors of which one-half of the designees are appointed by S1 and one-half of the designees are appointed by Fundtech), (2) changes in the composition and concentration of ownership of the combined company’s shares, and (3) the fact that the transaction constitutes a “change in control” under compensation arrangements for S1’s top management.

     Changes in S1’s Board and Management: According to S1’s proxy statement, following the Proposed Fundtech Merger, the governance of S1 would change as follows:

     • Fundtech’s CEO would become “Executive Chairman” of the combined company. Fundtech’s Chairman would become “Deputy Chairman” of the combined company. Fundtech’s CFO would become CFO of the combined company. One or more of these individuals apparently would serve in these capacities from Israel, and not S1’s principal U.S. offices.

     • S1’s Board would not constitute a majority of the Board of the combined company; rather, the combined company Board would be comprised of eight members, four from the current Board of Fundtech and four from the current Board of S1.

     • For an apparently indeterminate period, Fundtech’s CEO, as “Executive Chairman” of the combined company, and the combined company’s CEO would have to mutually agree before S1 could take any of the following actions. Disputes as to the following matters could only be resolved by the vote of a majority of the Board of the combined company, on which the current Fundtech directors will have a blocking vote:

• subject to certain exceptions, the issuance of any equity interests of the combined company or its subsidiaries or any securities exercisable or exchangeable for or convertible into equity interests of the combined company or its subsidiaries;

• incurrence of any indebtedness for borrowed money, other than indebtedness (i) outstanding as of the closing date of the Proposed Fundtech Merger or (ii) incurred in the ordinary course of business;

• engaging in any merger, consolidation or other business combination transactions or recapitalization or reorganization;

• acquisition of any enterprise or business (whether by merger, stock or assets) or other significant assets outside of the ordinary course of business;

• sale or other disposition of any assets of the combined company or any of its subsidiaries outside of the ordinary course of business;

• acquisition or development of any material new product or service offering;

• engaging in any line of business substantially different from those lines of business conducted by the combined company and its subsidiaries immediately following the closing date of the Proposed Fundtech Merger;

• hiring or termination of the executive chairman, chief executive officer, chief financial officer, chief operating officer, chief legal officer and each individual (including any consultant or other individual, even if not technically an employee) performing the functions of any such office, each referred to as a Senior Officer, or any individual who directly reports (including any consultant or other individual, even if not technically an employee) to any Senior Officer, referred to, together with the Senior Officers, each as an Applicable Employee;

• modification of the salary or other compensation of any Applicable Employee, materially changing the responsibilities of any Applicable Employee, or making any material changes to the employment agreement of any Applicable Employee;

• approval of (i) any operating or capital expenditure budget of the combined company or any of its subsidiaries or (ii) any material amendment or supplement to or other modification thereof;

• institution, settlement, withdrawal or compromise of any material lawsuit, claim, counterclaim or other legal proceeding by or against the combined company or any of its subsidiaries or with respect to any of their respective material properties or assets; or

• delegate any authority to take any of the foregoing actions to any other officer or employee.

     Changes in the Composition and Concentration of Share Ownership: The Proposed Fundtech Merger will result in a change in the composition and concentration in ownership of S1 Shares. According to a Schedule 13D filed in respect of Fundtech, Clal owns approximately 58% of Fundtech’s ordinary shares. Clal is controlled by the following four individuals: Nochi Dankner, Shelly Danker-Bergman, Isaac Manor and Avraham Livnat, who may be deemed to beneficially own the Fundtech shares held by Clal.

     According to S1’s proxy statement, Clal will own approximately 24% of the combined company, and by virtue of such ownership “may exert considerable influence over the combined company’s policies, business and affairs, and in any corporate transaction or other matter, including mergers, consolidations and the sale of all or substantially all of [S1’s] assets. This concentration in control may have the effect of delaying, deterring or preventing a change of control that otherwise would yield a premium upon the price of the combined company’s common stock. This concentration of ownership may also have the effect of reducing the amount of stock in the combined company’s public float, which may impact share trading values.”

     Although S1 stockholders will continue to own 55% of S1 Shares following the Proposed Fundtech Merger, these shares are held by a wide and diverse group of institutional and other investors and, based on reported share ownership as of August 29, 2011, no S1 stockholder other than Clal will own more than 5.0% of the outstanding S1 Shares if the Proposed Fundtech Merger were to be completed. The S1 Board exempted Clal from the restrictions applicable to “interested stockholders” under Section 203 of the Delaware General Corporation Law and has not otherwise restricted Clal’s ability to acquire additional shares or take actions in respect of the governance of S1 following the Proposed Fundtech Merger. Accordingly, Clal may be able to exert considerable influence over S1’s affairs following the Proposed Fundtech Merger as a result of its 24% ownership interest.

     “Change in Control” for the Benefit of S1 Top Management: The Proposed Fundtech Merger will constitute a “change of control” for purposes of the employment agreements, equity incentive plans and golden parachutes of S1’s senior management, resulting in the acceleration of certain benefits as described in S1’s proxy statement under the section titled “Interests of the Company’s Executive Officers and Directors in the Merger.”

     Based upon (1) the expected roles to be played by S1’s and Fundtech’s management following the Proposed Fundtech Merger in the combined company, (2) the substantial ownership of the combined company by Fundtech’s largest stockholder following the merger, and (3) the treatment of the merger as a “change of control” under the compensation arrangement of S1’s management, we believe that the Proposed Fundtech Merger looks much more like a change of control rather than an “acquisition” of Fundtech or a “merger”.

     In any case, we believe that S1’s Board, in evaluating any strategic transaction of this type, has a legal obligation to consider all available alternative transactions beforehand, to communicate those alternatives to S1’s stockholders and to consider our proposal which we believe provides superior value to S1’s stockholders.

     We believe S1 stockholders should take all of these factors into account prior to deciding whether to tender shares pursuant to the Exchange Offer, whether to exercise withdrawal rights as provided herein and, with respect to the election, whether to receive the Cash Consideration or the Stock Consideration or some combination thereof.

THE EXCHANGE OFFER

Overview

     Offeror is offering to exchange for each outstanding S1 Share that is validly tendered and not properly withdrawn prior to the Expiration Time, either of the following:

	•		0.2800 of an ACI Share (Stock Consideration); or
	•		$10.00 in cash, without interest (Cash Consideration),

subject to the proration procedures described in this prospectus/offer to exchange and the related letter of election and transmittal, upon the terms and subject to the conditions contained in this prospectus/offer to exchange and the accompanying letter of election and transmittal. In addition, you will receive cash in lieu of any fractional ACI Share to which you may be entitled.

     The term “Expiration Time” means 5:00 p.m., Eastern time, on Wednesday, September 28, 2011, unless Offeror extends the period of time for which the Exchange Offer is open, in which case the term “Expiration Time” means the latest time and date on which the Exchange Offer, as so extended, expires.

     The Exchange Offer is subject to conditions which are described in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer.” ACI expressly reserves the right, subject to the applicable rules and regulations of the SEC, to waive any condition of the Exchange Offer described herein in its discretion, except for the conditions described under the subheadings “Registration Statement Condition,” “NASDAQ Listing Condition,” and “Competition Condition” in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” below, each of which cannot be waived. Offeror expressly reserves the right to make any changes to the terms and conditions of the Exchange Offer (subject to any obligation to extend the Exchange Offer pursuant to the applicable rules and regulations of the SEC).

     If you are the record owner of your S1 Shares and you tender your S1 Shares in the Exchange Offer, you will not have to pay any brokerage fees or similar expenses. If you own your S1 Shares through a broker, dealer, commercial bank, trust company or other nominee and your broker, dealer, commercial bank, trust company or other nominee tenders your S1 Shares on your behalf, your broker or such other nominee may charge a fee for doing so. You should consult your broker, dealer, commercial bank, trust company or other nominee to determine whether any charges will apply.

     The purpose of the Exchange Offer is for ACI to acquire control of, and ultimately the entire equity interest in, S1. ACI has publicly expressed a desire to enter into a consensual business combination with S1 and delivered the Original ACI Merger Proposal to S1 on July 26, 2011 and the Enhanced ACI Merger Proposal to S1 on August 25, 2011.

     S1 announced on August 2, 2011 that the S1 Board would not discuss our the Original ACI Merger Proposal with us based on the S1 Board’s determination that pursuing discussions with ACI at this time is not in the best financial or strategic interests of S1 and its stockholders.

     On August 25, 2011, ACI publicly announced the Enhanced ACI Merger Proposal increasing the cash consideration payable under the Original ACI Merger Proposal by $0.50 per S1 Share, assuming full proration. Because the S1 Board has not begun negotiations with us, we have made this Exchange Offer without discussing it with S1.

     ACI, through Offeror, intends, promptly following acceptance for exchange and exchange of S1 Shares in the Exchange Offer, to effect the Second-Step Merger in accordance with Delaware law pursuant to which Offeror will acquire all S1 Shares of those S1 stockholders who choose not to tender their S1 Shares pursuant to the Exchange Offer. After the Second-Step Merger, former remaining S1 stockholders will no longer have any ownership interest in S1 and will be stockholders of ACI to the extent they receive any Stock Consideration in this Exchange Offer, and ACI, through Offeror, will own all of the issued and outstanding S1 Shares.

     Please see the sections of this prospectus/offer to exchange titled “The Exchange Offer—Purpose and Structure of the Exchange Offer”; “The Exchange Offer—Second-Step Merger”; and “The Exchange Offer—Plans for S1.”

     Subject to applicable law, Offeror reserves the right to amend the Exchange Offer (including by amending the consideration to be offered in the Exchange Offer or Second-Step Merger or the structure of the Second-Step Merger), including upon entering into a merger agreement with S1 (including a merger agreement that does not contemplate an exchange offer), in which event Offeror would terminate the Exchange Offer and the S1 Shares would, upon consummation of such acquisition, be exchanged for the merger consideration pursuant to the merger agreement. Please see the sections of this prospectus/offer to exchange titled “The Exchange Offer—Plans for S1” and “The Exchange Offer—Extension, Termination and Amendment.”

     Based on ACI’s and S1’s respective capitalizations as of August 29, 2011 and the estimated 5.9 million ACI Shares estimated to be issued in the Exchange Offer and the Second-Step Merger, former S1 stockholders would own, in the aggregate, approximately 14.4% of the aggregate ACI Shares on a fully diluted basis. For a detailed discussion of the assumptions on which this estimate is based, please see the section of this prospectus/offer to exchange titled “The Exchange Offer—Ownership of ACI After the Exchange Offer.”

Expiration Time of the Exchange Offer

     The Exchange Offer is scheduled to expire at 5:00 p.m., Eastern time, on Wednesday, September 28, 2011, which is the Expiration Time, unless further extended by Offeror. For more information, you should read the discussion below in the section of this prospectus/offer to exchange titled “The Exchange Offer—Extension, Termination and Amendment.”

Extension, Termination and Amendment

     Subject to the applicable rules of the SEC and the terms and conditions of the Exchange Offer, Offeror also expressly reserves the right (but will not be obligated) (1) to extend, for any reason, the period of time during which the Exchange Offer is open, (2) to delay acceptance for exchange of, or exchange of, S1 Shares in order to comply in whole or in part with applicable law (any such delay shall be effected in compliance with Rule 14e-1(c) under the Exchange Act, which requires Offeror to pay the consideration offered or to return S1 Shares deposited by or on behalf of S1 stockholders promptly after the termination or withdrawal of the Exchange Offer), (3) to terminate the Exchange Offer without accepting for exchange, or exchanging, any S1 Shares if any of the individually subheaded conditions referred to in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” has not been satisfied immediately prior to the Expiration Time or if any event specified in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” under the subheading “Other Conditions” has occurred; (4) to amend or terminate the Exchange Offer without accepting for exchange or exchanging any S1 Shares if ACI or any of its affiliates enters into a definitive agreement or announces an agreement in principle with S1 providing for a merger or other business combination or transaction with or involving S1 or any of its subsidiaries, or the purchase or exchange of securities or assets of S1 or any of its subsidiaries, or ACI and S1 reach any other agreement or understanding, in either case, pursuant to which it is agreed or provided that the Exchange Offer will be terminated; and (5) to amend the Exchange Offer or to waive any conditions to the Exchange Offer at any time, in each case by giving oral or written notice of such delay, termination, waiver or amendment to the exchange agent and by making public announcement thereof.

     The Expiration Time may also be subject to multiple extensions and any decision to extend the Exchange Offer, and if so, for how long, will be made prior to the Expiration Time.

     Any such extension, delay, termination, waiver or amendment will be followed as promptly as practicable by public announcement thereof, which, in the case of an extension, will be made no later than 9:00 a.m., Eastern time, on the next business day after the previously scheduled Expiration Time. Subject to applicable law (including Rules 14d-4(d)(i), 14d-6(c) and 14e-1 under the Exchange Act, which require that material changes be promptly disseminated to S1 stockholders in a manner reasonably designed to inform them of such changes), and without limiting the manner in which Offeror may choose to make any public announcement, Offeror will have no obligation to publish, advertise or otherwise communicate any such public announcement other than by issuing a press release or other announcement.

     Rule 14e-1(c) under the Exchange Act requires Offeror to pay the consideration offered or return the S1 Shares tendered promptly after the termination or withdrawal of the Exchange Offer.

     If ACI increases or decreases the percentage of S1 Shares being sought or the consideration offered in the Exchange Offer and the Exchange Offer is scheduled to expire at any time before the expiration of 10 business days from, and including, the date that notice of such increase or decrease is first published, sent or given in the manner specified below, the Exchange Offer will be extended until at least the expiration of 10 business days from, and including, the date of such notice. If Offeror makes a material change in the terms of the Exchange Offer (other than a change in the consideration offered in the Exchange Offer or the percentage of securities sought) or in the information concerning the Exchange Offer, or waives a material condition of the Exchange Offer, Offeror will extend the Exchange Offer, if required by applicable law, for a period sufficient to allow S1 stockholders to consider the amended terms of the Exchange Offer. In a published release, the SEC has stated its view that an offer must remain open for a minimum period of time following a material change in the terms of such offer, and that the waiver of a condition such as the condition described in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” under the subheading “Minimum Tender Condition” is a material change in the terms of an offer. The release states that an offer should remain open for a minimum of five business days from the date that the material change is first published, sent or given to S1 stockholders, and that if material changes are made with respect to information that approaches the significance of the price to be paid in the Exchange Offer or the percentage of shares sought in the Exchange Offer, a minimum of 10 business days may be required to allow adequate dissemination and investor response.

     As used in this prospectus/offer to exchange, a “business day” means any day, other than a Saturday, Sunday or a federal holiday, and shall consist of the time period from 12:01 a.m. through 12:00 midnight, Eastern time. If, prior to the Expiration Time, ACI increases the consideration being paid for S1 Shares accepted for exchange pursuant to the Exchange Offer, such increased consideration will be received by all S1 stockholders whose S1 Shares are exchanged pursuant to the Exchange Offer, whether or not such S1 Shares were tendered prior to the announcement of the increase of such consideration.

     Pursuant to Rule 14d-11 under the Exchange Act, Offeror may, subject to certain conditions, elect to provide a subsequent offering period of at least three business days following the Expiration Time on the date of the Expiration Time and acceptance for exchange of the S1 Shares tendered in the Exchange Offer. A subsequent offering period would be an additional period of time, following the first exchange of S1 Shares in the Exchange Offer, during which stockholders could tender S1 Shares not tendered in the Exchange Offer.

     During a subsequent offering period, tendering S1 stockholders would not have withdrawal rights and Offeror would promptly exchange and pay for any S1 Shares tendered at the same price paid in the Exchange Offer. Rule 14d-11 under the Exchange Act provides that Offeror may provide a subsequent offering period so long as, among other things, (1) the initial period of at least 20 business days of the Exchange Offer has expired, (2) Offeror offers the same form and amount of consideration for S1 Shares in the subsequent offering period as in the initial offer, (3) Offeror immediately accepts and promptly pays for all S1 Shares tendered prior to the Expiration Time, (4) ACI announces the results of the Exchange Offer, including the approximate number and percentage of S1 Shares deposited in the Exchange Offer, no later than 9:00 a.m., Eastern time, on the next business day after the Expiration Time and immediately begins the subsequent offering period, and (5) Offeror immediately accepts and promptly pays for S1 Shares as they are tendered during the subsequent offering period. If Offeror elects to include a subsequent offering period, it will notify S1 stockholders by making a public announcement on the next business day after the Expiration Time consistent with the requirements of Rule 14d-11 under the Exchange Act.

     Pursuant to Rule 14d-7(a)(2) under the Exchange Act, no withdrawal rights apply to S1 Shares tendered during a subsequent offering period and no withdrawal rights apply during a subsequent offering period with respect to S1 Shares tendered in the Exchange Offer and accepted for exchange. The same consideration will be received by S1 stockholders tendering S1 Shares in the Exchange Offer or in a subsequent offering period, if one is included. Please see the section of this prospectus/offer to exchange titled “The Exchange Offer—Withdrawal Rights.”

     This prospectus/offer to exchange, the letter of election and transmittal and all other relevant materials will be mailed by ACI to record holders of S1 Shares and will be furnished to brokers, dealers, banks, trust companies and similar persons whose names, or the names of whose nominees, appear on S1’s stockholders lists, or, if

applicable, who are listed as participants in a clearing agency’s security position listing for subsequent transmittal to beneficial owners of S1 Shares on or about August 30, 2011.

Acceptance for Exchange and Exchange of S1 Shares; Delivery of Exchange Offer Consideration

     Upon the terms and subject to the conditions of the Exchange Offer (including, if the Exchange Offer is extended or amended, the terms and conditions of any such extension or amendment), Offeror will accept for exchange promptly after the Expiration Time all S1 Shares validly tendered (and not withdrawn in accordance with the procedure set out in the section of this prospectus/offer to exchange titled “The Exchange Offer—Withdrawal Rights”) prior to the Expiration Time. Offeror will exchange all S1 Shares validly tendered and not withdrawn promptly following the acceptance of S1 Shares for exchange pursuant to the Exchange Offer. Offeror expressly reserves the right, in its discretion, but subject to the applicable rules of the SEC, to delay acceptance for and thereby delay exchange of S1 Shares in order to comply in whole or in part with applicable laws or if any of the conditions referred to in the section of this prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” have not been satisfied or if any event specified in the section of the prospectus/offer to exchange titled “The Exchange Offer—Conditions of the Exchange Offer” under the subheading “Other Conditions” has occurred. If Offeror decides to include a subsequent offering period, Offeror will accept for exchange, and promptly exchange, all validly tendered S1 Shares as they are received during the subsequent offering period. Please see the section of this prospectus/offer to exchange titled “The Exchange Offer—Withdrawal Rights.”

     In all cases (including during any subsequent offering period), Offeror will exchange all S1 Shares tendered and accepted for exchange pursuant to the Exchange Offer only after timely receipt by the exchange agent of (1) the certificates evidencing such S1 Shares or timely confirmation (a “Book-Entry Confirmation”) of a book-entry transfer of such S1 Shares into the exchange agent’s account at The Depository Trust Company pursuant to the procedures set forth in the section of this prospectus/offer to exchange titled “The Exchange Offer—Procedure for Tendering,” (2) the letter of election and transmittal (or a manually signed facsimile thereof), properly completed and duly executed, with any required signature guarantees, or, in the case of a book-entry transfer, an Agent’s Message (as defined below), and (3) any other documents required under the letter of election and transmittal. This prospectus/offer to exchange refers to The Depository Trust Company as the “Book-Entry Transfer Facility.” As used in this prospectus/offer to exchange, the term “Agent’s Message” means a message, transmitted by the Book-Entry Transfer Facility to, and received by, the exchange agent and forming a part of the Book-Entry Confirmation which states that the Book-Entry Transfer Facility has received an express acknowledgment from the participant in the Book-Entry Transfer Facility tendering the S1 Shares that are the subject of such Book-Entry Confirmation, that such participant has received and agrees to be bound by the letter of election and transmittal and that ACI may enforce such agreement against such participant.

     For purposes of the Exchange Offer (including during any subsequent offering period), Offeror will be deemed to have accepted for exchange, and thereby exchanged, S1 Shares validly tendered and not properly withdrawn as, if and when Offeror gives oral or written notice to the exchange agent of Offeror’s acceptance for exchange of such S1 Shares pursuant to the Exchange Offer. Upon the terms and subject to the conditions of the Exchange Offer, exchange of S1 Shares accepted for exchange pursuant to the Exchange Offer will be made by deposit of the Exchange Offer consideration being exchanged therefor with the exchange agent, which will act as agent for tendering S1 stockholders for the purpose of receiving the Exchange Offer consideration from Offeror and transmitting such consideration to tendering S1 stockholders whose S1 Shares have been accepted for exchange.

     Under no circumstances will Offeror pay interest on the Exchange Offer consideration for S1 Shares, regardless of any extension of the Exchange Offer or other delay in making such exchange or distributing the Exchange Offer consideration.

     If any tendered S1 Shares are not accepted for exchange for any reason pursuant to the terms and conditions of the Exchange Offer, or if certificates representing such S1 Shares are submitted evidencing more S1 Shares than are tendered, certificates evidencing unexchanged or untendered S1 Shares will be returned, without expense to the tendering S1 stockholder (or, in the case of S1 Shares tendered by book-entry transfer into the exchange agent’s account at a Book-Entry Transfer Facility pursuant to the procedure set forth in the section of this prospectus/offer to exchange titled “The Exchange Offer—Procedure for Tendering,” such S1 Shares will be credited to an account maintained at such Book-Entry Transfer Facility), as promptly as practicable following the expiration or termination of the Exchange Offer. ACI reserves the right to transfer or assign, in whole or from time

to time in part, to one or more of its affiliates, the right to exchange all or any portion of the S1 Shares tendered pursuant to the Exchange Offer, but any such transfer or assignment will not relieve Offeror of its obligations under the Exchange Offer or prejudice the rights of tendering stockholders to exchange S1 Shares validly tendered and accepted for exchange pursuant to the Exchange Offer.

Cash In Lieu of Fractional ACI Shares

     ACI will not issue certificates representing fractional ACI Shares pursuant to the Exchange Offer. Instead, each tendering S1 stockholder who would otherwise be entitled to a fractional ACI Share will receive cash (rounded to the nearest whole cent) in an amount (without interest) equal to the product obtained by multiplying (a) the fractional share interest to which such S1 stockholder would otherwise be entitled (after rounding such amount to the nearest 0.0001 share), by (b) the closing price of ACI Shares as reported on the NASDAQ Global Select Market on the last trading day prior to the Expiration Time.

Elections and Proration

     Based on the reported 55.5 million S1 Shares outstanding, in the Exchange Offer, ACI would exchange approximately $344.2 million cash and 5.9 million ACI Shares, of which approximately 34.4 million S1 Shares (62.0%) would be exchanged for the Cash Consideration and the remaining approximately 21.1 million S1 Shares (38.0%) would be exchanged for the Stock Consideration. S1 stockholders electing either the Cash Consideration or the Stock Consideration will be subject to proration so that not more than 62.0% of S1 Shares will be exchanged for the Cash Consideration and 38.0% of S1 Shares will be exchanged for the Stock Consideration in the Exchange Offer. S1 stockholders who do not participate in the Exchange Offer and whose shares are acquired in the Second-Step Merger will receive the Proration Amount of Cash and Stock Consideration. The elections of other S1 stockholders will affect whether a tendering S1 stockholder electing the Cash Consideration or the Stock Consideration receives solely the type of consideration elected or if a portion of such S1 stockholder’s tendered S1 Shares is exchanged for another form of consideration. S1 stockholders who otherwise would be entitled to receive a fractional ACI Share will instead receive cash in lieu of any fractional ACI Share such holder may have otherwise been entitled to receive.

Over-Subscription of Stock Election Shares

     If more than 38.0% of the S1 Shares tendered in the Exchange Offer (the “Stock Election Number”) elect to receive the Stock Consideration (each, a “Stock Election Share”), then:

	•		each S1 Share that is not a Stock Election Share (each, a “Non-Stock Share”) will be exchanged for $10.00 in cash, without interest;
	•		a number of Stock Election Shares of each stockholder making a stock election equal to the product of (x) the Cash Proration Factor and (y) the total number of Stock Election Shares held by such stockholder, will be exchanged for $10.00 in cash, without interest; and
	•		each Stock Election Share that has not been exchanged for $10.00 in cash, without interest in accordance with the preceding bullet will be exchanged for 0.2800 of an ACI Share.

Subscription of Stock Election Shares Equals Stock Election Number

     If the aggregate number of Stock Election Shares is equal to the Stock Election Number, then each Stock Election Share will be exchanged for 0.2800 of an ACI Share, and each Non-Stock Share will be exchanged for $10.00 in cash, without interest.

Under-Subscription of Stock Election Shares

     If the aggregate number of Stock Election Shares is less than 38.0% of the S1 Shares tendered in the Exchange Offer, then:

•

each Stock Election Share will be exchanged for 0.2800 of an ACI Share;

	•		a number of Non-Stock Shares of each stockholder equal to the product of (x) the Stock Proration Factor and (y) the total number of Non-Stock Shares of such stockholder, will be exchanged for 0.2800 of an ACI Share; and
	•		each Non-Stock Share that has not been exchanged for 0.2800 of an ACI Share pursuant to the preceding bullet will be exchanged for $10.00 in cash, without interest.

For purposes of these calculations:

	•		“Cash Proration Factor” means the quotient of (i) the excess of the total number of Stock Election Shares over the Stock Election Number divided by (ii) the total number of Stock Election Shares.
	•		“Stock Proration Factor” means the quotient of (i) the excess of the Stock Election Number over the total number of Stock Election Shares divided by (ii) the total number of Non-Stock Shares.

Consequences of Tendering with No Election

     S1 stockholders who do not make an election will be deemed to have elected the Cash Consideration.

Procedure for Tendering

     In order for a holder of S1 Shares to tender S1 Shares pursuant to the Exchange Offer, the exchange agent must receive, prior to the Expiration Time, the letter of election and transmittal (or a manually signed facsimile thereof), properly completed and duly executed, together with any required signature guarantees or, in the case of a book-entry transfer, an Agent’s Message, and any other documents required by such letter of election and transmittal, at one of its addresses set forth on the back cover of this prospectus/offer to exchange and either (1) the certificates evidencing tendered S1 Shares must be received by the exchange agent at such address or such S1 Shares must be tendered pursuant to the procedure for book-entry transfer described below and a Book-Entry Confirmation must be received by the exchange agent (including an Agent’s Message), in each case prior to the Expiration Time or the expiration of the subsequent offering period, if one is provided, or (2) the tendering S1 stockholder must comply with the guaranteed delivery procedures described below.

     The method of delivery of share certificates and all other required documents, including delivery through the Book-Entry Transfer Facility, is at the option and risk of the tendering S1 stockholder, and the delivery will be deemed made only when actually received by the exchange agent. If delivery is by mail, registered mail with return receipt requested, properly insured, is recommended. In all cases, sufficient time should be allowed to ensure timely delivery.

     Book-Entry Transfer. The exchange agent will establish accounts with respect to the S1 Shares at the Book-Entry Transfer Facility for purposes of the Exchange Offer within two business days after the date of this prospectus/offer to exchange. Any financial institution that is a participant in the system of the Book-Entry Transfer Facility may make a book-entry delivery of S1 Shares by causing the Book-Entry Transfer Facility to transfer such S1 Shares into the exchange agent’s account at the Book-Entry Transfer Facility in accordance with the Book-Entry Transfer Facility’s procedures for such transfer. However, although delivery of S1 Shares may be effected through book-entry transfer at the Book-Entry Transfer Facility, an Agent’s Message and any other required documents must, in any case, be received by the exchange agent at one of its addresses set forth on the back cover of this prospectus/offer to exchange prior to the Expiration Time or the expiration of the subsequent offering period, if one is provided, or the tendering S1 stockholder must comply with the guaranteed delivery procedures described below. Delivery of documents to the Book-Entry Transfer Facility does not constitute delivery to the exchange agent.

     Signature Guarantees. No signature guarantee is required on a letter of election and transmittal (1) if a letter of election and transmittal is signed by a registered holder of S1 Shares who has not completed the box titled “Special Issuance Instructions” on the letter of election and transmittal or (2) if S1 Shares are tendered for the account of a financial institution that is a member of the Securities Transfer Agents Medallion Signature Program, or by any other “Eligible Guarantor Institution,” as such term is defined in Rule 17Ad-15 under the Exchange Act (each of the foregoing being referred to as an “Eligible Institution”). In all other cases, all signatures on letters of transmittal must be guaranteed by an Eligible Institution.

If a certificate evidencing S1 Shares is registered in the name of a person other than the signer of a letter of election and transmittal, then such certificate must be endorsed or accompanied by appropriate stock powers, in either case signed exactly as the name(s) of the registered holder(s) appear on the share certificate, with the signature(s) on such certificate or stock powers guaranteed by an Eligible Institution. See Instructions 1 and 5 of the letter of election and transmittal.

     Guaranteed Delivery. If an S1 stockholder desires to tender S1 Shares pursuant to the Exchange Offer and such S1 stockholder’s certificate(s) evidencing such S1 Shares are not immediately available, such S1 stockholder cannot deliver such certificates and all other required documents to the exchange agent prior to the Expiration Time, or such S1 stockholder cannot complete the procedure for delivery by book-entry transfer on a timely basis, such S1 Shares may nevertheless be tendered, provided that all the following conditions are satisfied:

     (1) such tender is made by or through an Eligible Institution;

     (2) a properly completed and duly executed Notice of Guaranteed Delivery, substantially in the form made available by Offeror, is received prior to the Expiration Time by the exchange agent as provided below; and

     (3) the share certificates (or a Book-Entry Confirmation) evidencing all tendered S1 Shares, in proper form for transfer, in each case together with the letter of election and transmittal (or a manually signed facsimile thereof), properly completed and duly executed, with any required signature guarantees or, in the case of a book-entry transfer, an Agent’s Message, and any other documents required by the letter of election and transmittal are received by the exchange agent within three NASDAQ trading days after the date of execution of such Notice of Guaranteed Delivery.

     The Notice of Guaranteed Delivery may be delivered by hand or mail or by facsimile transmission to the exchange agent and must include a guarantee by an Eligible Institution in the form set forth in such Notice of Guaranteed Delivery. The procedures for guaranteed delivery above may not be used during any subsequent offering period.

     In all cases (including during any subsequent offering period), exchanges of S1 Shares tendered and accepted for exchange pursuant to the Exchange Offer will be made only after timely receipt by the exchange agent of the certificates evidencing such S1 Shares, or a Book-Entry Confirmation of the delivery of such S1 Shares (except during any subsequent offering period), and the letter of election and transmittal (or a manually signed facsimile thereof), properly completed and duly executed, with any required signature guarantees or, in the case of a book-entry transfer, an Agent’s Message, and any other documents required by the letter of election and transmittal.

     Determination of Validity. Offeror’s interpretation of the terms and conditions of the Exchange Offer (including the letter of election and transmittal and the instructions thereto) will be final and binding to the fullest extent permitted by law. All questions as to the form of documents and the validity, form, eligibility (including time of receipt) and acceptance for exchange of any tender of S1 Shares will be determined by Offeror, in its discretion, which determination shall be final and binding to the fullest extent permitted by law. Offeror reserves the absolute right to reject any and all tenders determined by it not to be in proper form or the acceptance of or exchange for which may, in the opinion of its counsel, be unlawful. Offeror also reserves the absolute right to waive any condition of the Exchange Offer to the extent permitted by applicable law or any defect or irregularity in the tender of any S1 Shares of any particular S1 stockholder, whether or not similar defects or irregularities are waived in the case of other S1 stockholders. No tender of S1 Shares will be deemed to have been validly made until all defects and irregularities have been cured or waived. None of ACI, Offeror or any of their affiliates or assigns, the dealer manager, the exchange agent, the information agent or any other person will be under any duty to give any notification of any defect or irregularity in tenders or to waive any such defect or irregularity or incur any liability for failure to give any such notification or waiver.

     A tender of S1 Shares pursuant to any of the procedures described above will constitute the tendering S1 stockholder’s acceptance of the terms and conditions of the Exchange Offer, as well as the tendering S1 stockholder’s representation and warranty to Offeror that (1) such S1 stockholder owns the tendered S1 Shares (and any and all other S1 Shares or other securities issued or issuable in respect of such S1 Shares), (2) such S1 stockholder has the full power and authority to tender, sell, assign and transfer the

tendered S1 Shares (and any and all other S1 Shares or other securities issued or issuable in respect of such S1 Shares) and (3) when the same are accepted for exchange, Offeror will acquire good, marketable and unencumbered title thereto, free and clear of all liens, restrictions, charges and encumbrances and not subject to any adverse claims.

     The acceptance for exchange by Offeror of S1 Shares pursuant to any of the procedures described above will constitute a binding agreement between the tendering S1 stockholder and Offeror upon the terms and subject to the conditions of the Exchange Offer, including with respect to the release and discharge from certain claims as described in the letter of election and transmittal.

     Appointment as Proxy; Other Agreements. By executing the letter of election and transmittal, or through delivery of an Agent’s Message, as set forth above, a tendering S1 stockholder irrevocably appoints designees of Offeror as such S1 stockholder’s agents, attorneys-in-fact and proxies, each with full power of substitution, in the manner set forth in such letter of election and transmittal, to the full extent of such S1 stockholder’s rights with respect to the S1 Shares tendered by such S1 stockholder and accepted for exchange by Offeror (and with respect to any and all other S1 Shares or other securities issued or issuable in respect of such S1 Shares on or after the date of this prospectus/offer to exchange). All such powers of attorney and proxies shall be considered irrevocable and coupled with an interest in the tendered S1 Shares (and such other S1 Shares and securities). Such appointment will be effective when, and only to the extent that, Offeror accepts such S1 Shares for exchange. Upon appointment, all prior powers of attorney and proxies given by such S1 stockholder with respect to such S1 Shares (and such other S1 Shares and securities) will be revoked, without further action, and no subsequent powers of attorney or proxies may be given nor any subsequent written consent executed by such S1 stockholder (and, if given or executed, will not be deemed to be effective) with respect thereto. The designees of Offeror will, with respect to the S1 Shares (and such other S1 Shares and securities) for which the appointment is effective, be empowered to exercise all voting, consent and other rights of such S1 stockholder as they in their discretion may deem proper at any annual or special meeting of S1 stockholders or any adjournment or postponement thereof, by written consent in lieu of any such meeting or otherwise. Offeror reserves the right to require that, in order for S1 Shares to be deemed validly tendered, immediately upon Offeror’s acceptance of S1 Shares for exchange, ACI must be able to exercise full voting, consent and other rights with respect to such S1 Shares (and such other S1 Shares and securities).

     The foregoing proxies are effective only upon acceptance for exchange of S1 Shares tendered pursuant to the Exchange Offer. The Exchange Offer does not constitute a solicitation of proxies (absent an exchange of S1 Shares) for any meeting of S1 stockholders, which will be made only pursuant to separate proxy materials complying with the requirements of the rules and regulations of the SEC. ACI reserves the right to solicit proxies or consents against the Proposed Fundtech Merger or to cause the S1 Board to be reconstituted with independents proposed by ACI independently of or in connection with the Exchange Offer.

     Backup Withholding. Under the “backup withholding” provisions of federal income tax law, the exchange agent may be required to withhold (currently at a rate of 28%) on any cash payments pursuant to the Exchange Offer or the Second-Step Merger. In order to prevent backup withholding with respect to payments to certain S1 stockholders for S1 Shares sold pursuant to the Exchange Offer or exchanged pursuant to the Second-Step Merger, each such S1 stockholder must timely provide the exchange agent with such S1 stockholder’s correct taxpayer identification number (the “TIN”) and certify that such stockholder is not subject to backup withholding by completing the substitute Form W-9 in the letter of election and transmittal, or otherwise establish an exemption. Certain S1 stockholders (including, among others, all corporations and certain non-U.S. individuals and entities) are not subject to backup withholding. If an S1 stockholder does not provide timely its correct TIN or fails to provide the certifications described above, the Internal Revenue Service may impose a penalty on the stockholder and payment of cash to the S1 stockholder pursuant to the Exchange Offer or the Second-Step Merger may be subject to backup withholding. All S1 stockholders surrendering S1 Shares pursuant to the Exchange Offer or the Second-Step Merger that are U.S. persons for federal income tax purposes should complete and sign the substitute Form W-9 included in the letter of election and transmittal to provide the information necessary to avoid backup withholding. Non-U.S. S1 stockholders should complete and sign an applicable Form W-8 (a copy of which may be obtained from the exchange agent) in order to avoid backup withholding.

Withdrawal Rights

     Tenders of S1 Shares made pursuant to the Exchange Offer are irrevocable except that such S1 Shares may be withdrawn at any time prior to the Expiration Time and, if Offeror has not accepted your S1 Shares for exchange by the Expiration Time, at any time following 60 days from commencement of the Exchange Offer. If Offeror elects to extend the Exchange Offer, is delayed in its acceptance for exchange of S1 Shares or is unable to accept S1 Shares for exchange pursuant to the Exchange Offer for any reason, then, without prejudice to ACI’s or Offeror’s rights under the Exchange Offer, the exchange agent may, on behalf of Offeror, retain tendered S1 Shares, and such S1 Shares may not be withdrawn except to the extent that tendering S1 stockholders are entitled to withdrawal rights as described in this section. Any such delay will be by an extension of the Exchange Offer to the extent required by law. If Offeror decides to include a subsequent offering period, S1 Shares tendered during the subsequent offering period may not be withdrawn. Please see the section of this prospectus/offer to exchange titled “The Exchange Offer—Extension, Termination and Amendment.”

     For a withdrawal to be effective, a written or facsimile transmission notice of withdrawal must be received by the exchange agent at one of its addresses set forth on the back cover page of this prospectus/offer to exchange. Any such notice of withdrawal must specify the name of the person who tendered the S1 Shares to be withdrawn, the number of S1 Shares to be withdrawn and the name of the registered holder of such S1 Shares, if different from that of the person who tendered such S1 Shares. If certificates evidencing S1 Shares to be withdrawn have been delivered or otherwise identified to the exchange agent, then, prior to the physical release of such certificates, the serial numbers shown on such certificates must be submitted to the exchange agent and, unless such S1 Shares have been tendered by or for the account of an Eligible Institution, the signature(s) on the notice of withdrawal must be guaranteed by an Eligible Institution. If S1 Shares have been tendered pursuant to the procedure for book-entry transfer as set forth in the section of this prospectus/offer to exchange titled “The Exchange Offer—Procedure for Tendering,” any notice of withdrawal must specify the name and number of the account at the Book-Entry Transfer Facility to be credited with the withdrawn S1 Shares.

     Withdrawals of S1 Shares may not be rescinded. Any S1 Shares properly withdrawn will thereafter be deemed not to have been validly tendered for purposes of the Exchange Offer. However, withdrawn S1 Shares may be re-tendered at any time prior to the Expiration Time (or during the subsequent offering period, if one is provided) by following one of the procedures described in the section of this prospectus/offer to exchange titled “The Exchange Offer—Procedure for Tendering” (except S1 Shares may not be re-tendered using the procedures for guaranteed delivery during any subsequent offering period).

     All questions as to the form and validity (including time of receipt) of any notice of withdrawal will be determined by Offeror, in its discretion, whose determination will be final and binding to the fullest extent permitted by law. None of ACI, Offeror or any of their respective affiliates or assigns, the dealer manager, the exchange agent, the information agent or any other person will be under any duty to give any notification of any defect or irregularity in any notice of withdrawal or incur any liability for failure to give any such notification.

Announcement of Results of the Exchange Offer

     ACI will announce the final results of the Exchange Offer, including whether all of the conditions to the Exchange Offer have been fulfilled or waived and whether Offeror will accept the tendered S1 Shares for exchange after the Expiration Time. The announcement will be made by a press release.

Ownership of ACI After the Exchange Offer

     Based on ACI’s and S1’s respective capitalizations as of August 29, 2011 and assuming ACI issues 5.9 million ACI Shares pursuant to the Exchange Offer and the Second-Step Merger, former S1 stockholders would own, in the aggregate, approximately 14.4% of the aggregate ACI Shares on a fully diluted basis.

Certain Material Federal Income Tax Consequences

     The following is a general summary of the material United States Federal income tax consequences to S1 stockholders that exchange S1 Shares for ACI Shares and/or cash pursuant to the Exchange Offer and the Second-

Step Merger. This discussion is based on provisions of the Internal Revenue Code, Treasury regulations promulgated thereunder, and administrative and judicial interpretations thereof, all as in effect as of the date hereof and all of which are subject to change, possibly with retroactive effect. This discussion does not address all aspects of United States Federal income taxation that may be applicable to S1 stockholders in light of their particular circumstances or to S1 stockholders subject to special treatment under United States Federal income tax law including, without limitation:

	•		partnerships;
	•		foreign persons;
	•		certain financial institutions;
	•		insurance companies;
	•		tax-exempt entities;
	•		dealers in securities;
	•		traders in securities that elect to apply a mark-to-market method of accounting;
	•		certain U.S. expatriates;
	•		persons that hold S1 Shares as part of a straddle, hedge, conversion transaction or other integrated investment;
	•		S1 stockholders whose functional currency is not the United States dollar; and
	•		S1 stockholders who acquired S1 Shares through the exercise of employee stock options or otherwise as compensation.