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                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM 8-K

                                 CURRENT REPORT

                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

         Date of Report (Date of earliest event reported): March 1, 2006

                                 S1 CORPORATION
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             (Exact name of registrant as specified in its charter)

             Delaware                 000-24931           58-2395199
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   (State or other jurisdiction      (Commission        (IRS Employer
         of incorporation)           File Number)     Identification No.)

               3500 Lenox Road, Suite 200, Atlanta, Georgia 30326
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                    (Address of principal executive offices)

       Registrant's telephone number, including area code: (404) 923-3500

                                 NOT APPLICABLE
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          (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):

[ ]  Written communications pursuant to Rule 425 under the Securities
     Act (17 CFR 230.425)

[ ]  Soliciting material pursuant to Rule 14a-12 under the Exchange
     Act (17 CFR 240.14a-12)

[ ]  Pre-commencement communications pursuant to Rule 14d-2(b) under the
     Exchange Act (17 CFR 240.14d-2(b))

[ ]  Pre-commencement communications pursuant to Rule 13e-4(c) under the
     Exchange Act (17 CFR 240.13e-4(c)) Rule 425, Rule 14a-12 and Instruction 2
     to Rule 14d-2(b)(2)

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ITEM 2.02   RESULTS OF OPERATIONS AND FINANCIAL CONDITION

        On March 1, 2006, S1 Corporation ("S1") issued a press release
announcing the results of operations for the fourth quarter and full year ended
December 31, 2005. That press release is furnished as Exhibit 99.1 to this
report. Also on March 1, 2006, S1 held a conference call during which S1
discussed its fourth quarter and full year results and presented certain other
material relating to S1 and its operations. A replay of the conference call is
available for playback two hours after the conference call is complete by
dialing (800) 642-1687, ID 5614427. The replay will be active until 5:00 p.m.
EST on March 8, 2006.

        In accordance with General Instruction B.2 of Form 8-K, the information
in this Current Report on Form 8-K, including Exhibit 99.1, shall not be deemed
"filed" for the purposes of Section 18 of the Securities Exchange Act of 1934,
as amended, or otherwise subject to the liability of that section, nor shall it
be deemed incorporated by reference in any filing under the Securities Act of
1933, as amended, except as shall be expressly set forth by specific reference
in such a filing.

ITEM 9.01   FINANCIAL STATEMENTS AND EXHIBITS

(d) Exhibits

Exhibit No.     Description
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   99.1         Press release dated March 1, 2006.



                                   SIGNATURES

        Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                                   S1 CORPORATION
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                                                   (Registrant)


                                                   /s/ Richard P. Dobb
                                                   -----------------------------
                                                   Richard P. Dobb
                                                   Vice President,
                                                   General Counsel and Secretary

Date: March 1, 2006



                                  EXHIBIT INDEX

Exhibit No.     Description
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   99.1         Press release dated March 1, 2006.