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. 1)

                                   ----------

                      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

                                   ----------

/ / 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.

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



This Amendment No. 1 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 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 10.  FINANCIAL STATEMENTS.

Item 10 of the Tender Offer Statement is amended to add the following
sentence: The information set forth in Exhibit (a)(9) identified in Item 12
and attached hereto is also incorporated herein by reference.

ITEM 12.  EXHIBITS.

Item 12 of the Tender Offer Statement is hereby amended as follows:

A.       Paragraph (K) on page 4 of Exhibit (a)(2) is hereby deleted in its
         entirety and will not be enforced by TSA with respect to any Acceptance
         Letters that have been or will be tendered to TSA.

B.       References to Exhibits (a)(9), (a)(10), (a)(11), (a)(12), (a)(13),
         (a)(14), and (a)(15), which are attached hereto, are added as follows:

         (a)(9)  Supplemental Information Concerning Offer to Exchange.

         (a)(10) Form of Cover Letter to Employees and Directors Accompanying
                 Supplemental Information Concerning Offer to Exchange.

         (a)(11) Form of Cover Letter to Employees in Australia Accompanying
                 Supplemental Information Concerning Offer to Exchange.

         (a)(12) Form of Cover Letter to Employees in Canada Accompanying
                 Supplemental Information Concerning Offer to Exchange.

         (a)(13) Form of Cover Letter to Employees in Singapore Accompanying
                 Supplemental Information Concerning Offer to Exchange.

         (a)(14) Form of Cover Letter to Employees in The Netherlands
                 Accompanying Supplemental Information Concerning Offer to
                 Exchange.

         (a)(15) Form of Reminder E-mail - August   , 2001.



                                  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 13, 2001



                                INDEX TO EXHIBITS

EXHIBIT NUMBER DESCRIPTION - ------- ----------- (a)(9) Supplemental Information Concerning Offer to Exchange. (a)(10) Form of Cover Letter to Employees and Directors Accompanying Supplemental Information Concerning Offer to Exchange. (a)(11) Form of Cover Letter to Employees in Australia Accompanying Supplemental Information Concerning Offer to Exchange. (a)(12) Form of Cover Letter to Employees in Canada Accompanying Supplemental Information Concerning Offer to Exchange. (a)(13) Form of Cover Letter to Employees in Singapore Accompanying Supplemental Information Concerning Offer to Exchange. (a)(14) Form of Cover Letter to Employees in The Netherlands Accompanying Supplemental Information Concerning Offer to Exchange. (a)(15) Form of Reminder E-mail - August , 2001.


                                                                 Exhibit (a)(9)

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

                                 August 13, 2001

To:      All Eligible Employees and Eligible Directors of Transaction Systems
         Architects, Inc. ("TSA") under the Offer to Exchange, dated August 1,
         2001

Re:      Supplemental Information Concerning the Offer to Exchange

         This memorandum provides supplemental information concerning the Offer
to Exchange, as follows. Pursuant to this supplement, we are amending Section 9
of the Offer to Exchange ("Information Concerning TSA") to add certain summary
financial information concerning TSA. This supplement does not alter the terms
and conditions previously set forth in the Offer to Exchange, and should be read
in conjunction with the Offer to Exchange.

                                 * * * * * * * *

         The following tables set forth selected financial and operating data of
TSA. The selected historical statement of operations data for the years ended
September 30, 1999 and 2000 and the selected historical balance sheet data as of
September 30, 1999 and 2000 have been derived from the audited financial
statements included in our annual report on Form 10-K for the year ended
September 30, 2000. The selected historical statement of operations data for
the nine months ended June 30, 2000 and June 30, 2001 and the selected
historical balance sheet data as of June 30, 2001 are unaudited and will be
included in our quarterly report for the quarter ended June 30, 2001. The
information presented below should be read together with our financial
statements and related notes filed as an Exhibit to our annual report on Form
10-K and our other SEC filings referred to in Section 16 ("Additional
Information").



                             Selected Financial Data
       (in accordance with U.S. generally accepted accounting principles)
             (in thousands of U.S. dollars except per share amounts)

                                   (Unaudited)

For the year ended For the nine month period September 30, ended June 30, 2000 1999 2001 2000 ---- ---- ---- ---- Results of Operations Total revenues $303,565 $354,794 $224,799 $221,408 Operating income (loss) 1,742 70,260 (24,614) 533 Net income (loss) 2,111 44,700 (39,471) 1,183 Net income (loss) per common share - basic 0.07 1.41 (1.17) 0.04 - diluted 0.07 1.38 (1.17) 0.04
As at September 30, As at June 30, 2000 1999 2001 ---- ---- ---- Financial Position Current assets $173,773 $179,816 $168,580 Noncurrent assets 156,379 143,502 172,772 Current liabilities 105,267 85,675 105,718 Noncurrent liabilities 14,525 12,474 12,869 Book value per common share 6.65 7.01 6.34
In addition, our earnings of $44.7 million covered our fixed charges of $401,000 by a ratio of 111.47% for the fiscal year ended September 30, 1999 and our earnings of $2.11 million covered our fixed charges of $912,000 by a ratio of 2.31% for the fiscal year ended September 30, 2000. However, our earnings of $(39.471) million for the nine months ended June 30, 2001 were inadequate to cover our fixed charges of $(1.717) million for that period.


                                                                Exhibit (a)(10)

                                  AMENDMENT TO

                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                   OFFER TO EXCHANGE 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

                                 FOR NEW OPTIONS

                     THE OFFER AND WITHDRAWAL RIGHTS EXPIRE

            AT 11:59 P.M., OMAHA, NEBRASKA TIME, ON AUGUST 28, 2001,

          UNLESS TRANSACTION SYSTEMS ARCHITECTS, INC. EXTENDS THE OFFER

Dear Option Holder:

         As you are aware, Transaction Systems Architects, Inc. commenced its
stock option exchange program on August 1, 2001. Today, important
supplemental information concerning the Offer to Exchange, dated August 1,
2001 is being distributed to you. Please review this supplemental
information. In addition, if you have not already done so, please review the
Offer to Exchange.

         If you decide to tender options pursuant to the Offer to Exchange,
you must properly complete, sign, and submit the related Acceptance Letter
for receipt by us NO LATER THAN 11:59 P.M., Omaha, Nebraska time, TUESDAY,
AUGUST 28, 2001, by external mail. DELIVERY BY FACSIMILE, E-MAIL, OR ANY FORM
OF INTEROFFICE MAIL WILL NOT BE ACCEPTED.

         You should direct any questions about the offer or requests for
assistance or additional copies of the Offer to Exchange or the Acceptance
Letter to:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No.: (402) 778-1911
                         E-mail Address: nippe@tsain.com




         To tender your options for exchange, properly complete and sign the
Acceptance Letter in accordance with instructions, and send the Acceptance
Letter and any other required documents to us by external mail to:

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

         We recommend that you use a courier service or registered mail with
return receipt requested. Delivery by facsimile, e-mail, or any form of
interoffice mail with NOT be accepted.

                                      Transaction Systems Architects, Inc.

                                      August 13, 2001



                                                                Exhibit (a)(11)

                                  AMENDMENT TO

                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                   OFFER TO EXCHANGE 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

                                 FOR NEW OPTIONS

                     THE OFFER AND WITHDRAWAL RIGHTS EXPIRE

            AT 11:59 P.M., OMAHA, NEBRASKA TIME, ON AUGUST 28, 2001,

          UNLESS TRANSACTION SYSTEMS ARCHITECTS, INC. EXTENDS THE OFFER

Dear Option Holder:

         As you are aware, Transaction Systems Architects, Inc. commenced its
stock option exchange program on August 1, 2001. Today, important
supplemental information concerning the Offer to Exchange, dated August 1,
2001 is being distributed to you. Please review this supplemental
information. In addition, if you have not already done so, please review the
Offer to Exchange.

         If you decide to tender options pursuant to the Offer to Exchange,
you must properly complete, sign, and submit the related Acceptance Letter
for receipt by us NO LATER THAN 11:59 P.M., Omaha, Nebraska time, TUESDAY,
AUGUST 28, 2001, by external mail. DELIVERY BY FACSIMILE, E-MAIL, OR ANY FORM
OF INTEROFFICE MAIL WILL NOT BE ACCEPTED.

         Offers to eligible employees in Australia to participate in the
stock option exchange program were accompanied by the principle Offer to
Exchange document and supplementary document entitled "Addendum for Employees
in Australia". If you are eligible to participate in the stock option
exchange program and wish to participate, you will need to complete the
Acceptance Letter attached to the Offer to Exchange.




         You should direct any questions about the offer or requests for
assistance or additional copies of the Offer to Exchange or the Acceptance
Letter to:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No.: (402) 778-1911
                         E-mail Address: nippe@tsain.com

         To tender your options for exchange, properly complete and sign the
Acceptance Letter in accordance with instructions, and send the Acceptance
Letter and any other required documents to us by external mail to:

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

         We recommend that you use a courier service or registered mail with
return receipt requested. Delivery by facsimile, e-mail, or any form of
interoffice mail with NOT be accepted.

                                        Transaction Systems Architects, Inc.

                                        August 13, 2001



                                                                Exhibit (a)(12)

                                  AMENDMENT TO

                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                   OFFER TO EXCHANGE 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

                                 FOR NEW OPTIONS

                     THE OFFER AND WITHDRAWAL RIGHTS EXPIRE

            AT 11:59 P.M., OMAHA, NEBRASKA TIME, ON AUGUST 28, 2001,

          UNLESS TRANSACTION SYSTEMS ARCHITECTS, INC. EXTENDS THE OFFER

Dear Option Holder:

         As you are aware, Transaction Systems Architects, Inc. commenced its
stock option exchange program on August 1, 2001. Today, important
supplemental information concerning the Offer to Exchange, dated August 1,
2001 is being distributed to you. Please review this supplemental
information. In addition, if you have not already done so, please review the
Offer to Exchange.

         If you decide to tender options pursuant to the Offer to Exchange,
you must properly complete, sign, and submit the related Acceptance Letter
for receipt by us NO LATER THAN 11:59 P.M., Omaha, Nebraska time, TUESDAY,
AUGUST 28, 2001, by external mail. DELIVERY BY FACSIMILE, E-MAIL, OR ANY FORM
OF INTEROFFICE MAIL WILL NOT BE ACCEPTED.

         Offers to eligible employees in Canada to participate in the stock
option exchange program were accompanied by the principle Offer to Exchange
document and supplementary document entitled "Addendum for Employees in
Canada". If you are eligible to participate in the stock option exchange
program and wish to participate, you will need to complete the Acceptance
Letter attached to the Offer to Exchange.




         You should direct any questions about the offer or requests for
assistance or additional copies of the Offer to Exchange or the Acceptance
Letter to:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No.: (402) 778-1911
                         E-mail Address: nippe@tsain.com

         To tender your options for exchange, properly complete and sign the
Acceptance Letter in accordance with instructions, and send the Acceptance
Letter and any other required documents to us by external mail to:

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

         We recommend that you use a courier service or registered mail with
return receipt requested. Delivery by facsimile, e-mail, or any form of
interoffice mail with NOT be accepted.

                                      Transaction Systems Architects, Inc.

                                      August 13, 2001



                                                                Exhibit (a)(13)

                                  AMENDMENT TO

                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                   OFFER TO EXCHANGE 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

                                 FOR NEW OPTIONS

                     THE OFFER AND WITHDRAWAL RIGHTS EXPIRE

            AT 11:59 P.M., OMAHA, NEBRASKA TIME, ON AUGUST 28, 2001,

          UNLESS TRANSACTION SYSTEMS ARCHITECTS, INC. EXTENDS THE OFFER

Dear Option Holder:

         As you are aware, Transaction Systems Architects, Inc. commenced its
stock option exchange program on August 1, 2001. Today, important
supplemental information concerning the Offer to Exchange, dated August 1,
2001 is being distributed to you. Please review this supplemental
information. In addition, if you have not already done so, please review the
Offer to Exchange.

         If you decide to tender options pursuant to the Offer to Exchange,
you must properly complete, sign, and submit the related Acceptance Letter
for receipt by us NO LATER THAN 11:59 P.M., Omaha, Nebraska time, TUESDAY,
AUGUST 28, 2001, by external mail. DELIVERY BY FACSIMILE, E-MAIL, OR ANY FORM
OF INTEROFFICE MAIL WILL NOT BE ACCEPTED.

         Offers to eligible employees in Singapore to participate in the
stock option exchange program were accompanied by the principle Offer to
Exchange document and supplementary document entitled "Addendum for Employees
in Singapore". If you are eligible to participate in the stock option
exchange program and wish to participate, you will need to complete the
Acceptance Letter attached to the Offer to Exchange.




         You should direct any questions about the offer or requests for
assistance or additional copies of the Offer to Exchange or the Acceptance
Letter to:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No.: (402) 778-1911
                         E-mail Address: nippe@tsain.com

         To tender your options for exchange, properly complete and sign the
Acceptance Letter in accordance with instructions, and send the Acceptance
Letter and any other required documents to us by external mail to:

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

         We recommend that you use a courier service or registered mail with
return receipt requested. Delivery by facsimile, e-mail, or any form of
interoffice mail with NOT be accepted.

                                        Transaction Systems Architects, Inc.

                                        August 13, 2001



                                                                Exhibit (a)(14)

                                  AMENDMENT TO

                      TRANSACTION SYSTEMS ARCHITECTS, INC.

                   OFFER TO EXCHANGE 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

                                 FOR NEW OPTIONS

                     THE OFFER AND WITHDRAWAL RIGHTS EXPIRE

            AT 11:59 P.M., OMAHA, NEBRASKA TIME, ON AUGUST 28, 2001,

          UNLESS TRANSACTION SYSTEMS ARCHITECTS, INC. EXTENDS THE OFFER

Dear Option Holder:

         As you are aware, Transaction Systems Architects, Inc. commenced its
stock option exchange program on August 1, 2001. Today, important
supplemental information concerning the Offer to Exchange, dated August 1,
2001 is being distributed to you. Please review this supplemental
information. In addition, if you have not already done so, please review the
Offer to Exchange.

         If you decide to tender options pursuant to the Offer to Exchange,
you must properly complete, sign, and submit the related Acceptance Letter
for receipt by us NO LATER THAN 11:59 P.M., Omaha, Nebraska time, TUESDAY,
AUGUST 28, 2001, by external mail. DELIVERY BY FACSIMILE, E-MAIL, OR ANY FORM
OF INTEROFFICE MAIL WILL NOT BE ACCEPTED.

         Offers to eligible employees in The Netherlands to participate in
the stock option exchange program were accompanied by the principle Offer to
Exchange document and supplementary document entitled "Addendum for Employees
in The Netherlands". If you are eligible to participate in the stock option
exchange program and wish to participate, you will need to complete the
Acceptance Letter attached to the Offer to Exchange.




         You should direct any questions about the offer or requests for
assistance or additional copies of the Offer to Exchange or the Acceptance
Letter to:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No.: (402) 778-1911
                         E-mail Address: nippe@tsain.com

         To tender your options for exchange, properly complete and sign the
Acceptance Letter in accordance with instructions, and send the Acceptance
Letter and any other required documents to us by external mail to:

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

         We recommend that you use a courier service or registered mail with
return receipt requested. Delivery by facsimile, e-mail, or any form of
interoffice mail with NOT be accepted.

                                     Transaction Systems Architects, Inc.

                                     August 13, 2001



                                                                Exhibit (a)(15)


Date:                      , August   , 2001

To:           Option Holders
Subject:      Stock Option Exchange Program Offer Expiration Date Approaches!

         Just a reminder to eligible employees and eligible directors who are
considering participating in the stock option exchange program that the
executed Acceptance Letter must be received by external mail NO LATER THAN
11:59 P.M., Omaha, Nebraska time, on Tuesday, August 28, 2001. Remember, once
the offer expires, there will NOT be any other opportunity to submit an
acceptance or a withdrawal in connection with the stock option exchange
program.

         The program was described in the Offer to Exchange dated August 1,
2001 that was distributed to each eligible employee and eligible director.
Also, for those eligible employees located in Australia, Canada, Singapore and
The Netherlands, the Offer to Exchange was accompanied by supplementary
documents entitled "Addendum for Employees in Australia", "Addendum for
Employees in Canada", "Addendum for Employees in Singapore", and "Addendum for
Employees in The Netherlands", respectively.

         For more information on the stock option exchange program, refer to
the package of materials you received by e-mail or regular mail or contact
the following person:

                                    Eric Nipp
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                          Telephone No: (402) 778-1911
                        E-mail Address: nippe@tsainc.com