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)

                                   ----------

                      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.