SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                                   SCHEDULE TO
                                 (RULE 14d-100)

            TENDER OFFER STATEMENT UNDER SECTION 14(d)(1) OR 13(e)(1)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                       (AMENDMENT NO. 4 - FINAL AMENDMENT)

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                      TRANSACTION SYSTEMS ARCHITECTS, INC.
         (Name of Subject Company (Issuer) and Filing Person (Offeror))

                                   ----------

      OPTIONS TO PURCHASE CLASS A COMMON STOCK, PAR VALUE $0.005 PER SHARE,
         GRANTED TO ELIGIBLE EMPLOYEES AND ELIGIBLE DIRECTORS UNDER THE
                ACI HOLDING, INC. 1994 STOCK OPTION PLAN AND THE
                      TRANSACTION SYSTEMS ARCHITECTS, INC.
                1996 STOCK OPTION PLAN AND 1999 STOCK OPTION PLAN
                         (Title of Class of Securities)

                                    893416107
                      (CUSIP Number of Class of Securities)

                                 David P. Stokes
                      Vice President - Legal and Secretary
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                                 (402) 334-5101

       (Name, Address and Telephone Number of Person Authorized to Receive
             Notices and Communications on Behalf of Filing Person)

                                   ----------

                                    Copy to:
                             Albert G. McGrath, Jr.
                                Baker & McKenzie
                          2001 Ross Avenue, Suite 2300
                               Dallas, Texas 75201
                                 (214) 978-3000
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[_] Check the box if the filing relates solely to preliminary communications
made before the commencement of a tender offer.

Check the appropriate boxes below to designate any transactions to which the
statement relates:

         [_] third party tender offer subject to Rule 14d-l.

         [X] issuer tender offer subject to Rule 13e-4.

         [_] going-private transaction subject to Rule 13e-3.

         [_] amendment to Schedule 13D under Rule 13d-2.

[X] Check the following box if the filing is a final amendment reporting the
results of the tender offer.



This Amendment No. 4 amends and supplements the Tender Offer Statement on
Schedule TO (the "Tender Offer Statement") filed by Transaction Systems
Architects, Inc., a Delaware corporation ("TSA"), relating to the offer by TSA
to exchange certain outstanding employee and director options to purchase shares
of its common stock under the ACI Holding, Inc. 1994 Stock Option Plan and the
Transaction Systems Architects, Inc. 1996 Stock Option Plan and 1999 Stock
Option Plan for new options to purchase shares of its common stock, upon the
terms and subject to the conditions set forth in the Offer to Exchange, dated
August 1, 2001, as supplemented on August 13, 2001, and in the related
Acceptance Letter, copies of which were attached as Exhibits (a)(1) and (a)(2),
respectively, to the Tender Offer Statement.

ITEM 4.  TERMS OF THE TRANSACTION.

Item 4 of the Tender Offer Statement is hereby amended and supplemented as
follows:

The offer made by TSA pursuant to the Tender Offer Statement expired at 11:59
p.m., Omaha, Nebraska time, Tuesday, August 28, 2001. TSA accepted for exchange
and cancellation options to purchase an aggregate of approximately 1,941,050
shares of TSA's common stock, representing 63% of the options subject to the
offer. TSA expects to issue new options to purchase 1,941,050 shares of its
common stock in exchange for the options accepted for exchange and cancellation
as described in the Offer to Exchange.

ITEM 12.  EXHIBITS.

Item 12 of the Tender Offer Statement is hereby amended to add a reference to
Exhibit (a)(18), which is attached hereto, as follows:

         (a)(18)  Form of Letter Sent to Option Holders Following Expiration of
                  Offer Period and Cancellation of Tendered Options.




                                    SIGNATURE

         After due inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

                                       TRANSACTION SYSTEMS ARCHITECTS, INC.


                                       /s/ Dwight G. Hanson
                                       -----------------------------------------
                                       Dwight G. Hanson,
                                       Chief Financial Officer and Senior
                                       Vice President


DATE:  August 31, 2001







                                INDEX TO EXHIBITS

EXHIBIT NUMBER DESCRIPTION - ------ ----------- (a)(18) Form of Letter Sent to Option Holders Following Expiration of Offer Period and Cancellation of Tendered Options.


                                                                 Exhibit (a)(18)

                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154

                                 August 31, 2001


Dear Option Holder:

         On behalf of Transaction Systems Architects, Inc. ("TSA"), I am writing
to provide you with the results of TSA's recent offer to exchange outstanding
options granted under the ACI Holding, Inc. 1994 Stock Option Plan and the
Transaction Systems Architects, Inc. 1996 Stock Option Plan and 1999 Stock
Option Plan (collectively, the "Option Plans") for new options TSA will grant
under the Option Plans. The offer was consummated pursuant to the terms and
conditions in TSA's Offer to Exchange, dated August 1, 2001, as supplemented on
August 13, 2001, and the related Acceptance Letter.

         The offer expired at 11:59 p.m., Omaha, Nebraska time, on August 28,
2001. Promptly following the expiration of the offer and pursuant to the terms
and conditions of the offer, TSA accepted for exchange on August 29, 2001
tendered options exercisable for a total of 1,941,050 shares of its Class A
common stock, par value $0.005 per share (the "common stock"), and canceled all
such options tendered for exchange.

         TSA has accepted for exchange and canceled the options tendered by you
exercisable for the number of shares of common stock set forth on Attachment A
to this letter. In accordance with the terms and subject to the conditions of
the offer, you have the right to receive a new option under the same Option Plan
as the tendered options exercisable for the same number of shares of common
stock as the tendered options as set forth on Attachment A, as adjusted for any
stock splits, stock dividends and similar events that occur prior to the date on
which TSA issues such new options. Also in accordance with the terms of the
offer, the terms and conditions of the new options will generally be
substantially the same as the terms and conditions of the options you tendered
for exchange, except that:

o        the per share exercise price of the new options will equal the fair
         market value of the common stock on the date TSA grants the new
         options;

o        the new options will have an 18 month, monthly vesting schedule that
         will begin on the date TSA grants the new options, except that if
         executive officers tender options under the 1994 Option Plan, their new
         options will vest 25% annually on each anniversary of that grant date;
         and

o        the new options will expire ten years from the date TSA grants the new
         options, except that certain new options granted to residents of the
         United Kingdom may have an expiration date of seven years from that
         grant date.



         In accordance with the terms and subject to the conditions of the
offer, TSA will grant you the new options on or about March 4, 2002. At that
time, as described in the Offer to Exchange, you will receive a new option
agreement that will be executed by you and TSA.

         In accordance with the terms of the offer, and as provided in the
Option Plans, you must be an eligible employee or eligible director of TSA or
one of its subsidiaries from August 1, 2001 continuously through the date TSA
grants the new options to receive your new options. If for any reason you are
not an eligible employee or eligible director from August 1, 2001 continuously
through the date TSA grants the new options, you will not receive a new option
or any other consideration for the options tendered by you and cancelled by TSA.
Participation in the offer does not confer upon you the right to remain in the
employment or as a director of TSA or any of its subsidiaries.

         If you have any questions about your rights in connection with the
grant of a new option, please contact Eric Nipp at Transaction Systems
Architects, Inc., 224 South 108th Avenue, Omaha, Nebraska 68154, (402) 778-1911,
nippe@tsainc.com.

                                                  Sincerely,

                                                  /s/ Lang G. Fendley







                                                  Attachment A



- ----------------------------------------------------------------------------------------------------------------- Number of Shares of Common Stock Exercise Price of Name of Subject to Tendered Option Tendered Option Option Holder Accepted for Exchange Accepted for Exchange Title of Option Plan - ----------------------------------------------------------------------------------------------------------------- - -----------------------------------------------------------------------------------------------------------------
Number of Shares of Common Stock Subject to New Options to be Granted to You on or About March 4, 2002: