EXHIBIT 4(c)

NEITHER THIS NOTE NOR THE SECURITIES WHICH MAY BE ISSUED UPON CONVERSION OF THIS
NOTE HAVE BEEN REGISTERED  UNDER THE SECURITIES ACT OF 1933, AS AMENDED,  OR ANY
APPLICABLE STATE SECURITIES  LAWS, BY REASON OF SPECIFIC  EXEMPTIONS  THEREUNDER
AND CANNOT BE SOLD, TRANSFERRED OR OTHERWISE DISPOSED OF TO ANY PERSON OR ENTITY
UNLESS  SUBSEQUENTLY  REGISTERED  THEREUNDER  OR  UNLESS  APPLICABLE  EXEMPTIONS
THEREFROM ARE AVAILABLE.


                       NATIONAL TRANSACTION NETWORK, INC.

                     CONVERTIBLE SUBORDINATED NOTE DUE 2002


$400,000                                                      September 19, 1997

         For value  received,  National  Transaction  Network,  Inc., a Delaware
corporation  (the "Company"),  hereby promises to pay to International  Verifact
Inc. or  registered  assigns  (hereinafter  referred to as the  "Payee"),  on or
before  September  18, 2002 (the "Due Date") the  principal  sum of Four Hundred
Thousand  dollars  ($400,000) or such part thereof as then remains unpaid and to
pay accrued and unpaid interest from the date hereof on the whole amount of said
principal sum remaining at the end of each quarter unpaid at a rate equal to The
First National Bank of Boston's best prime rate, as announced at the end of each
calendar quarter,  plus (i) 2% or (ii) 5% during any period which the Company is
in default of its  covenants  in respect of its working  capital  line of credit
with Silicon Valley Bank, in each case calculated and compounded on the last day
of each quarter,  such  interest to be payable  together with the payment of the
principal of this Note.  Principal and interest shall be payable in lawful money
of the United States of America at the principal  office of the Payee or at such
other place as the legal  holder may  designate  from time to time in writing to
the  Company.  Interest  shall be computed on the basis of a 360-day  year and a
90-day calendar quarter.

         This Note is issued  pursuant to and is  entitled to the  benefits of a
certain Convertible Subordinated Note Purchase Agreement, dated as of August 18,
1997,  between the Company and  International  Verifact Inc. (as the same may be
amended from time to time, hereinafter referred to as the "Agreement"), and each
holder  of this  Note,  by his  acceptance  hereof,  agrees  to be  bound by the
provisions  of the  Agreement,  including,  without  limitation,  that:  (i) the
principal  of and  interest  on this Note is  subordinated  to Senior  Debt,  as
defined in the Agreement, (ii) in case of an Event of Default, as defined in the
Agreement,  the  principal  of this Note may become or may be  declared  due and
payable in the manner and with the effect  provided in the  Agreement  and (iii)
this Note is  convertible  at the option of the  holder  hereof  into  shares of
Common Stock of the Company in the manner set forth in this Agreement.








         This Note is  secured  by and  entitled  to the  benefits  of a certain
Security  Agreement (as that term is defined in the Agreement),  dated September
19, 1997, from the Company to International Verifact Inc.

         In case any payment herein provided for shall not be paid when due, the
Company  promises  to pay  all  cost of  collection,  including  all  reasonable
attorney's fees.

         This Note shall be governed by, and construed in accordance  with,  the
laws of the Commonwealth of Massachusetts.

         The Company and all endorsers and  guarantors of this Note herein waive
presentment,  demand,  notice of  nonpayment,  protest and all other demands and
notices in connection with the delivery, acceptance,  performance or enforcement
of this Note.

                                        NATIONAL TRANSACTION NETWORK, INC.


                                        By:  /s/  Milton A. Alpern
                                             ----------------------------
                                                  Milton A. Alpern
                                        Vice President, Finance & Administration