

 
 
     As filed with the Securities and Exchange Commission on April 27, 1998
                              Registration No. 333-
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-4
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                      TRANSACTION SYSTEMS ARCHITECTS, INC.
             (Exact name of registrant as specified in its charter)

                                    Delaware
         (State or other jurisdiction of incorporation or organization)

                                      7372
            (Primary Standard Industrial Classification Code Number)

                                   47-0772104
                      (I.R.S. Employer Identification No.)

                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                                 (402) 334-5101
   (Address, including ZIP Code, and telephone number, including area code, of
                    registrant's principal executive offices)

                          William E. Fisher, President
                      Transaction Systems Architects, Inc.
                             224 South 108th Avenue
                              Omaha, Nebraska 68154
                                 (402) 334-5101
 (Name, address, including ZIP Code, and telephone number, including area code,
                            of agent for service)

            It is requested that copies of communications be sent to:
                                Neal A. Klegerman
                                Baker & McKenzie
                              One Prudential Plaza
                             Chicago, Illinois 60601

Approximate  date of  commencement  of proposed  sale of the  securities  to the
public:  As soon as practicable  after the effective  date of this  Registration
Statement.  

If the securities  being registered on this Form are being offered in connection
with the  formation of a holding  company and there is  compliance  with General
Instruction G, check the following box. [ ]

If this Form is filed to register additional securities for an offering pursuant
to Rule 462(b) under the  Securities  Act,  check the following box and list the
Securities  Act  registration   statement   number  of  the  earlier   effective
registration statement for the same offering. [X] 333-24279

If this Form is a  post-effective  amendment filed pursuant to Rule 462(d) under
the  Securities  Act,  check  the  following  box and  list the  Securities  Act
registration  statement number of the earlier effective  registration  statement
for the same offering. [ ]

If any of the  securities  being  registered on this Form are to be offered on a
delayed or continuous  basis  pursuant to Rule 415 under the  Securities  Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. [X]

<PAGE>

                         Calculation of Registration Fee
<TABLE>
<CAPTION>

--------------------------- ----------------------- ----------------------- ------------------------ -----------------------

                                                                                  Proposed
Title of each class                                      Proposed                  maximum
of securities to be              Amount to be          maximum offering        aggregate offering           Amount of
registered                        registered          price per unit (1)    price (1)                   registration fee
--------------------------- ----------------------- ----------------------- ------------------------ -----------------------
=========================== ======================= ======================= ======================== =======================
<S>                        <C>                     <C>                     <C>                      <C>                           
Class A Common Stock, par       224,264 shares             $38.875                  $8,718,263            $2.575
value $.005 per share
=========================== ======================= ======================= ======================== =======================
</TABLE>


(1)  Estimated  solely  for the  purpose of  calculating  the  registration  fee
pursuant  to Rule  457(c)  promulgated  under  the  Securities  Act of 1933,  as
amended, based upon the average of the high and low prices of the Class A Common
Stock  on  April 20, 1998,   as  reported  on  The  Nasdaq   National   Market.
                                
                                _______________
<PAGE>

     This  Registration  Statement is being filed  pursuant to Rule 462(b) under
the  Securities  Act of 1933,  as  amended.  The  contents  of the  Registration
Statement on Form S-4 (File No.  333-24279),  previously filed by the Registrant
and declared  effective by the  Commission on April 10, 1997,  are  incorporated
herein by reference.

     The required opinions and consents are listed on the Exhibit Index attached
hereto and filed herewith.
<PAGE>

                                   SIGNATURES

Pursuant to the  requirements  of the  Securities  Act, the  registrant has duly
caused  this  Registration   Statement  to  be  signed  on  its  behalf  by  the
undersigned, thereunto duly authorized, in the City of Omaha, State of Nebraska,
on April 27, 1998.

                                            TRANSACTION SYSTEMS ARCHITECTS, INC.


                                                    By:    /s/ Gregory J. Duman
                                                           --------------------
                                                               Gregory J. Duman
                                                        Chief Financial Officer


Pursuant to the  requirements of the Securities Act of 1933,  this  Registration
Statement has been signed by the following  persons in the capacities and on the
dates indicated.

   Name                       Title                                    Date
   ----                       -----                                    ----
          
         *               Director and President                   April 27, 1998
-----------------        (Principal Executive Officer)
William E. Fisher      


/s/ Gregory J. Duman    Chief Financial Officer                   April 27, 1998
--------------------    (Principal Financial Officer)
Gregory J. Duman      


        *               Vice President                            April 27, 1998
-----------------       (Principal Accounting Officer)
Dwight G. Hanson        


        *               Director                                  April 27, 1998
-----------------
David C. Russell


        *               Director                                  April 27, 1998
-----------------
Jim D. Kever


        *               Director                                  April 27, 1998
-----------------
Promod Haque


        *               Director                                  April 27, 1998
-----------------
Charles E. Noell, III


        *               Director                                  April 27, 1998
----------------
Larry G. Fendley


/s/ Gregory J. Duman                                              April 27, 1998
---------------------
*Gregory J. Duman as
Attorney-In-Fact Pursuant
to Power of Attorney
Granted in Registration
Statement No. 333-24279

<PAGE>

================================================================================
                                  EXHIBIT INDEX
================================================================================

 Exhibit
 Number                          Description                     
-------  ----------------------------------------------------------------------

5.01     Opinion of Baker & McKenzie

23.01    Consent of Independent Public Accountants

23.02    Consent of Baker & McKenzie (included in opinion filed as Exhibit 5.01)

24.01    Power  of  Attorney  (contained  in  Signature  Page to  Registration  
         Statement on Form S-4 (File No. 333-24279) and incorporated herein by 
         reference)
<PAGE>
