<PAGE>

                                                                   EXHIBIT 10.15
                          AGREEMENT REGARDING LEASES
                          --------------------------

          THIS AGREEMENT REGARDING LEASES (this "Agreement") is made and entered
into as of the _____ day of _______, 2001, by and between EQUIFAX INC., a
Georgia corporation ("Equifax"), and EQUIFAX PAYMENT SERVICES, INC., a Delaware
corporation ("the name of which entity will be changed to "Certegy Payment
Services, Inc.")("Certegy Payment Services").

                             W I T N E S S E T H:

          WHEREAS, Certegy Payment Services is currently a wholly-owned
subsidiary of Equifax;

          WHEREAS, Equifax presently intends to transfer and assign to Certegy
Inc., a Georgia corporation ("Certegy"), as a contribution to the capital of
Certegy, the capital stock of Certegy Payment Services and certain related
assets (the "Spin Transaction"); and

          WHEREAS, each of Certegy Payment Services and its subsidiaries
(collectively, the "Certegy Payment Services Group"; the persons and entities
composing the Certegy Payment Services Group are herein referred to as "Certegy
Payment Services Group Companies") and Equifax and its subsidiaries other than
those that compose the Certegy Payment Services Group Companies (collectively,
the "Equifax Group"; the persons and entities composing the Equifax Group are
herein referred to as "Equifax Group Companies") have entered into certain Lease
Agreements and Lease Guarantees, and the parties hereto desire to agree upon
certain matters with respect to such Lease Agreements and Lease Guarantees in
connection with the Spin Transaction, as set forth in this Agreement.

          NOW, THEREFORE, for and in consideration of the sum of Ten and No/100
Dollars ($10.00), the foregoing premises and the respective undertakings of the
parties, and other good and valuable consideration, the receipt and sufficiency
of which are hereby acknowledged, Equifax and Certegy Payment Services hereby
agree as follows:

          1.  Certegy Payment Services Group Leases; Equifax Guarantees.
              ---------------------------------------------------------

              (a) Certegy Payment Services Group Leases.  Certain Certegy
                  -------------------------------------
Payment Services Group Companies are currently the "tenants" or "lessees" under
those certain Lease Agreements identified on Exhibit "A" attached hereto and
                                             -----------
incorporated herein (the "Certegy Payment Services Group Leases"), and such
Certegy Payment Services Group Companies will continue to be the "tenants" or
"lessees" under their Lease Agreements immediately after the consummation of the
Spin Transaction. The parties intend that the Spin Transaction shall not
constitute an assignment or other transfer under any of the Certegy Payment
Services Group Leases that would require the consent of the "landlord" or
"lessor" thereunder, but, in the event the Spin Transaction is deemed to be such
an assignment or other transfer under any of the Certegy Payment Services Group
Leases, then Equifax and Certegy Payment Services hereby agree to reasonably
cooperate with each other in obtaining any such required consent of the
"landlord" or "lessor" thereunder. Certegy Payment Services shall, and hereby
agrees to, indemnify, defend and hold Equifax harmless from, against and in
respect of any
<PAGE>

actions, causes of action, suits, claims, demands, judgments, or proceedings
asserted against, imposed upon or suffered or incurred by Equifax, and from,
against and in respect of any liabilities, damages, losses, costs, expenses
(including counsel fees and expenses and disbursements of counsel), amounts of
judgment, assessments, fines or penalties, and amounts paid in compromise or
settlement, asserted against, imposed upon or suffered or incurred by Equifax,
in connection with or arising out of or by reason of any one or more of the
Certegy Payment Services Group Leases in connection with the Spin Transaction or
otherwise.

          (b) Equifax Guarantees.  Equifax has entered into lease guarantees
              ------------------
(the "Equifax Guarantees") with respect to the duties, obligations, liabilities,
and responsibilities of the "tenant" or "lessee" under certain of the Certegy
Payment Services Group Leases, as identified on Exhibit "B" attached hereto and
                                               -----------
incorporated herein. Certegy Payment Services shall, and hereby agrees to,
indemnify, defend and hold Equifax harmless from, against and in respect of any
actions, causes of action, suits, claims, demands, judgments, or proceedings
asserted against, imposed upon or suffered or incurred by Equifax, and from,
against and in respect of any liabilities, damages, losses, costs, expenses
(including counsel fees and expenses and disbursements of counsel), amounts of
judgment, assessments, fines or penalties, and amounts paid in compromise or
settlement, asserted against, imposed upon or suffered or incurred by Equifax in
connection with or arising out of or by reason of any one or more of the Equifax
Guarantees. Without limiting any of the rights or remedies of Equifax under the
Distribution Agreement (as hereinafter defined) or otherwise, Equifax shall be
subrogated to the right, title, and interest of the "landlord" or "lessor" under
each of the Equifax Guarantees and all rights or remedies of the "landlord" or
"lessor" thereunder to the extent Equifax is required to honor any such Equifax
Guarantees and to the extent permitted under the terms of the applicable Certegy
Payment Services Group Lease.

          2.  Equifax Group Leases; Subletting; Assignment.
              --------------------------------------------

          (a) Equifax Group Leases.  Certain Equifax Group Companies are
              --------------------
currently the "tenants" or "lessees" under those certain Lease Agreements
identified on Exhibit "C" attached hereto and incorporated herein (the "Equifax
              -----------
Group Leases"), and all or a portion of the premises under each of such Equifax
Group Leases are currently occupied by one or more Certegy Payment Services
Group Companies. The parties desire that portions of the premises under certain
Equifax Group Leases be sublet, and that certain of the Equifax Group Leases be
assigned, to the Certegy Payment Services Group Company currently occupying all
or a portion of the premises thereunder, as set forth in subparagraphs (b) and
(c), below.

          (b) Subletting.  Certegy Payment Services Group Companies currently
              ----------
occupy all or a portion of the premises under each of the Equifax Group Leases
identified as "to be sublet" on Exhibit "C" hereto, which occupied portion of
                                -----------
each such premises is more particularly described on said Exhibit "C".  Each of
                                                          -----------
the Equifax Group Companies that is the "tenant" or "lessee" under each such
Equifax Group Lease (each as a "Sublandlord" hereunder) does hereby sublease to
the Certegy Payment Services Company identified on said Exhibit "C" as the
                                                        -----------
"Subtenant" with respect to such Equifax Group Lease, and each such Subtenant
does hereby sublease from its respective Sublandlord, for the term and on the
terms and conditions hereinafter provided in Exhibit "D" attached hereto and
                                             -----------
incorporated herein, such portion of the premises under such

                                       2
<PAGE>

Equifax Group Lease as is more particularly described in said Exhibit "C", and
                                                              -----------
herein referred to, as the "Sublet Premises". For purposes of Exhibit "D" and
                                                              -----------
this Agreement, and with respect to each such Equifax Group Lease, the term
"Total Premises" means the entire "premises" under such Equifax Group Lease. In
the event any such subletting requires the consent of the "landlord" or "lessor"
under the applicable Equifax Group Lease, then the respective Sublandlord and
Subtenant hereby agree to reasonably cooperate with each other in obtaining any
such required consent. All statements, covenants, agreements, representations
and warranties, if any, made herein (including, without limitation, in Exhibit
                                                                       -------
"D" hereto) by each Sublandlord shall be deemed to be made by such party only
---
with respect to itself or to the Equifax Group Lease or Sublet Premises of such
party, as the case may be, and shall not be deemed to be made by such party with
respect to any other Sublandlord or to any other Equifax Group Lease or Sublet
Premises, and each Sublandlord shall have liability and responsibility under
this Agreement with respect to such subletting only in respect of the Sublet
Premises of that Sublandlord and shall have no liability or responsibility in
respect of any other Sublet Premises.

          (c) Assignment.  Certegy Payment Services Group Companies currently
              ----------
occupy all or a portion of the premises under each of the Equifax Group Leases
identified as "to be assigned" on Exhibit "C" hereto. Each of the Equifax Group
                                  -----------
Companies that is the "tenant" or "lessee" under each such Equifax Group Lease
(each as an "Assignor" hereunder) does hereby assign all of its right, title,
and interest in and to its respective Equifax Group Lease to the Certegy Payment
Services Company identified on said Exhibit "C" as the "Assignee" with respect
                                    -----------
to such Equifax Group Lease, and each such Assignee does hereby assume all of
the obligations, duties, responsibilities, and liabilities of the "tenant" or
"lessee" under such Equifax Group Lease with respect to periods of time from and
after the date of this Agreement, pursuant to and in accordance with the terms
and conditions hereinafter provided in Exhibit "E" attached hereto and
                                       -----------
incorporated herein. In the event any such assignment requires the consent of
the "landlord" or "lessor" under the applicable Equifax Group Lease, then the
respective Assignor and Assignee hereby agree to reasonably cooperate with each
other in obtaining any such required consent. All statements, covenants,
agreements, representations and warranties, if any, made herein (including,
without limitation, in Exhibit "E" hereto) by each Assignor shall be deemed to
                       -----------
be made by such party only with respect to itself or to the Equifax Group Lease
of such party, as the case may be, and shall not be deemed to be made by such
party with respect to any other Assignor or to any other Equifax Group Lease,
and each Assignor shall have liability and responsibility under this Agreement
with respect to such assignment only in respect of the Equifax Group Lease of
that Assignor and shall have no liability or responsibility in respect of any
other Equifax Group Lease.

          3.   Distribution Agreement.
               ----------------------

          (a) Compliance.  Certegy Payment Services shall comply with, abide
              ----------
by, and perform all of the terms, covenants, conditions, agreements,
requirements, restrictions and provisions of Section 2.08 of the Distribution
Agreement (as hereinafter defined) as to the Certegy Payment Services Group
Leases and the Equifax Guarantees and with respect to each Sublet Premises and
the subleasing and assignments set forth in this Agreement. The term
"Distribution Agreement"

                                       3
<PAGE>

means that certain Distribution Agreement dated as of the date of this Agreement
executed by and between Equifax and Certegy in connection with the Spin
Transaction.

          (b) Dispute Resolution.  Any disputes arising under this Agreement,
              ------------------
and any liability of either party with respect to the attorneys' fees or costs
incurred by the other party with respect to such dispute, shall be resolved in
accordance with Section 15.10 of the Distribution Agreement in the same manner
and with the same effect as if said Section were set forth in full and at length
herein and as if Certegy Payment Services and each Sublandlord and Assignee
hereunder were the parties thereto other than Equifax, and as if Equifax and
each Sublandlord and Assignor hereunder were the parties thereto other than
Certegy, and said Section is hereby incorporated herein.

          4.  Further Assurances.  From time to time after the date hereof, each
              ------------------
of Equifax and Certegy Payment Services, and any Sublandlord, Subtenant,
Assignor, and Assignee, shall, upon written request, do all such additional and
further acts, and shall execute and deliver all such additional and further
assignments, subleases, and other instruments and documents, as any other party
hereto may reasonably require to effectuate the terms and conditions of this
Agreement.

          5.  General Provisions.
              ------------------

          (a) Notices.  Whenever any notice, demand or request is required or
              -------
permitted to be given by one party hereto to the other party under this
Agreement, such notice, demand or request shall be in writing and shall be
delivered by hand, be sent by registered or certified mail, postage prepaid,
return receipt requested, or be sent by nationally recognized commercial courier
for next business day delivery, to the addresses set forth below such party's
respective execution hereof, or to such other addresses as are specified by
written notice given in accordance herewith.  All notices, demands or requests
delivered by hand shall be deemed given upon the date so delivered; those given
by mailing as hereinabove provided shall be deemed given on the date of deposit
in the United States Mail; and those given by commercial courier as hereinabove
provided shall be deemed given on the date of deposit with the commercial
courier.  Nonetheless, the time period, if any, in which a response to any
notice, demand or request must be given shall commence to run from the date of
receipt of the notice, demand or request by the addressee thereof.  Any notice,
demand or request not received because of changed address of which no notice was
given as hereinabove provided or because of refusal to accept delivery shall be
deemed received by the party to whom addressed on the date of hand delivery, on
the first business day after deposit with commercial courier, or on the third
business day following deposit in the United States Mail, as the case may be.

          (b) Headings.  The use of headings, captions and numbers in this
              --------
Agreement is solely for the convenience of identifying and indexing the various
provisions in this Agreement and shall in no event be considered otherwise in
construing or interpreting any provision in this Agreement.

          (c) Exhibits.  Each and every exhibit referred to or otherwise
              --------
mentioned in this Agreement is attached to this Agreement and is and shall be
construed to be made a part of

                                       4
<PAGE>

this Agreement by such reference or other mention at each point at which such
reference or other mention occurs, in the same manner and with the same effect
as if each exhibit were set forth in full and at length every time it is
referred to or otherwise mentioned.

          (d) Defined Terms.  Capitalized terms used in this Agreement shall
              -------------
have the meanings ascribed to them at the point where first defined,
irrespective of where their use occurs, with the same effect as if the
definitions of such terms were set forth in full and at length every time such
terms are used.

          (e) Pronouns.  Wherever appropriate in this Agreement, personal
              --------
pronouns shall be deemed to include the other genders and the singular to
include the plural.

          (f) Severability.  If any term, covenant, condition or provision of
              ------------
this Agreement, or the application thereof to any person or circumstance, shall
ever be held to be invalid or unenforceable, then in each such event the
remainder of this Agreement or the application of such term, covenant, condition
or provision to any other person or any other circumstance (other than those as
to which it shall be invalid or unenforceable) shall not be thereby affected,
and each term, covenant, condition and provision hereof shall remain valid and
enforceable to the fullest extent permitted by law.

          (g) Non-Waiver.  Failure by any party to complain of any action, non-
              ----------
action or breach of any other party shall not constitute a waiver of any
aggrieved party's rights hereunder. Waiver by any party of any right arising
from any breach of any other party shall not constitute a waiver of any other
right arising from a subsequent breach of the same obligation or for any other
default, past, present or future.

          (h) Rights Cumulative.  All rights, remedies, powers and privileges
              -----------------
conferred under this Agreement on the parties shall be cumulative of and in
addition to, but not restrictive of or in lieu of, those conferred by law or at
equity.

          (i) Time of Essence.  Time is of the essence of this Agreement.
              ---------------

          (j) Applicable Law.  This Agreement shall be governed by, construed
              --------------
under and interpreted and enforced in accordance with the laws of the State of
Georgia.

          (k) Entire Agreement; Modification.  This Agreement supersedes all
              ------------------------------
prior discussions and agreements between Equifax and Certegy Payment Services,
and any Sublandlord. Subtenant, Assignor, or Assignee, with respect to the
Certegy Payment Services Group Leases, the Equifax Group Leases, the Equifax
Guarantees, the subletting and assigning hereunder and other matters expressly
set forth herein, and this Agreement contains the sole and entire understanding
between Equifax and Certegy Payment Services, and the Sublandlords, Subtenants,
Assignors, and Assignees, with respect thereto. This Agreement shall not be
modified or amended except by an instrument in writing executed by or on behalf
of Equifax and Certegy Payment Services; provided, however, that if any such
                                         --------  -------
modification or amendment affects any subletting described in Section 2(b),
above, or any assignment described in Section 2(c), then the Sublandlord and

                                       5
<PAGE>

Subtenant or the Assignor and Assignee, as the case may be, shall also be a
party to such modification or amendment instrument.

          (l) Counterparts.  This Agreement may be executed in several
              ------------
counterparts, each of which shall be deemed an original, and all of such
counterparts together shall constitute one and the same instrument.

          (m) Authority.  Each party hereto warrants and represents that such
              ---------
party has full and complete authority to enter into this Agreement and each
person executing this Agreement on behalf of a party warrants and represents
that he has been fully authorized to execute this Agreement on behalf of such
party and that such party is bound by the signature of such representative.

          (n) No Construction Against Preparer.  No provision of this Agreement
              --------------------------------
shall be construed against or interpreted to the disadvantage of any party by
any court or other governmental or judicial authority by reason of such party's
having or being deemed to have prepared or imposed such provision.

          (o) Successors and Assigns.  This Agreement shall bind and benefit the
              ----------------------
successors and assigns of the parties with the same effect as if mentioned in
each instance where a party hereto is named or referred to.

                                       6
<PAGE>

     IN WITNESS WHEREOF, Equifax and Certegy Payment Services have caused their
duly authorized representatives to execute, seal and deliver this Agreement
Regarding Leases, all as of the day and year first written above.


                                  EQUIFAX:
                                  --------

                                  Equifax Inc., a Georgia corporation



Date executed:                    By:
               ----------------      ---------------------------------
                                     Name:
                                          ----------------------------
                                     Title:
                                           ---------------------------

                                                [CORPORATE SEAL]


                                  Initial Address for Notices:
                                  ----------------------------

                                  Equifax Inc.
                                  1550 Peachtree Street
                                  Atlanta, Georgia 30309
                                  Attn:  Phillip J. Mazzilli, CFO

                                  with a copy to:
                                  ---------------

                                  Equifax Inc.
                                  1550 Peachtree Street
                                  Atlanta, Georgia 30309
                                  Attn:  Kent E. Mast, General Counsel

                                       7
<PAGE>

                                  PAYMENT SERVICES:
                                  -----------------

                                  Equifax Payment Services, Inc., a Delaware
                                  corporation



Date executed:                    By:
               ----------------      ---------------------------------
                                     Name:
                                          ----------------------------
                                     Title:
                                           ---------------------------

                                                [CORPORATE SEAL]


                                  Initial Address for Notices:
                                  ---------------------------

                                  Equifax Payment Services, Inc.
                                  c/o Certegy Inc.

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

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

                                  Attn:  Michael T. Volkommer, CFO

                                  with a copy to:
                                  ---------------

                                  Equifax Payment Services, Inc.
                                  c/o Certegy Inc.

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

                                  ------------------------------------
                                  Attn:  Bruce S. Richards, General Counsel

                                       8
<PAGE>

         Agreement and Acknowledgment of Sublandlords and Subtenants:
         -----------------------------------------------------------

          Each of the following parties hereby agree to the terms and provisions
of the foregoing Agreement Regarding Leases, and is hereby made a party thereto,
solely with respect to the subleasing of the Sublet Premises with respect to
which such party is Sublandlord or Subtenant pursuant to Section 2(b) of the
foregoing Agreement Regarding Leases.


SUBLANDLORDS:                              SUBTENANTS:
-------------                              -----------

----------------------------------         ------------------------------------
Equifax Information Services LLC
(f/k/a Equifax Credit Information
Services, Inc.)

By:                                        By:
   -------------------------------            ---------------------------------
   Name:                                      Name:
        --------------------------                 ----------------------------
   Title:                                     Title:
         --------------------------                 ---------------------------
           [CORPORATE SEAL]                                 [CORPORATE SEAL]


----------------------------------         ------------------------------------
Equifax Knowledge Engineering, Inc.
(f/k/a Market Knowledge, Inc.)

By:                                        By:
   -------------------------------            ---------------------------------
   Name:                                      Name:
        --------------------------                 ----------------------------
   Title:                                     Title:
         --------------------------                 ---------------------------
           [CORPORATE SEAL]                                 [CORPORATE SEAL]


Initial Address for Notices for each       Initial Address for Notices for each
------------------------------------       ------------------------------------
Sublandlord:                               Subtenant:
-----------                                ---------

                                           [Name of Subtenant]
[Name of Sublandlord]                      c/o Certegy Inc.
c/o Equifax Inc.
1550 Peachtree Street                      ------------------------------------
Atlanta, Georgia 30309
Attn:  Phillip J. Mazzilli, CFO            ------------------------------------
                                           Attn:  Michael T. Volkommer, CFO
with a copy to:
---------------                            with a copy to:
                                           ---------------

[Name of Sublandlord]                      [Name of Subtenant]
c/o Equifax Inc.                            c/o Certegy Inc.
1550 Peachtree Street
Atlanta, Georgia 30309                     ------------------------------------
Attn:  Kent E. Mast, General Counsel
                                           ------------------------------------
                                           Attn: Bruce S. Richards,
                                                 General Counsel

<PAGE>

            Agreement and Acknowledgment of Assignors and Assignees:
            -------------------------------------------------------

          Each of the following parties hereby agree to the terms and provisions
of the foregoing Agreement Regarding Leases, and is hereby made a party thereto,
solely with respect to the assignment of the Equifax Group Lease with respect to
which such party is Assignor or Assignee pursuant to Section 2(c) of the
foregoing Agreement Regarding Leases.


ASSIGNORS:                                 ASSIGNEES:
---------                                  ---------

----------------------------------         ------------------------------------
Equifax Inc.

By:                                        By:
   -------------------------------            ---------------------------------
   Name:                                      Name:
        --------------------------                 ----------------------------
   Title:                                     Title:
         --------------------------                 ---------------------------
           [CORPORATE SEAL]                                 [CORPORATE SEAL]


----------------------------------         ------------------------------------
Equifax Information Services LLC
(f/k/a Equifax Credit Information
Services, Inc.)

By:                                        By:
   -------------------------------            ---------------------------------
   Name:                                      Name:
        --------------------------                 ----------------------------
   Title:                                     Title:
         --------------------------                 ---------------------------
           [CORPORATE SEAL]                                 [CORPORATE SEAL]


Initial Address for Notices for each       Initial Address for Notices for each
------------------------------------       ------------------------------------
Assignor:                                  Assignee:
--------                                   --------

                                           [Name of Assignee]
[Name of Assignor]                         c/o Certegy Inc.
c/o Equifax Inc.
1550 Peachtree Street                      ------------------------------------
Atlanta, Georgia 30309
Attn:  Phillip J. Mazzilli, CFO            ------------------------------------
                                           Attn:  Michael T. Volkommer, CFO
with a copy to:
---------------                            with a copy to:
                                           ---------------

[Name of Assignor]                         [Name of Assignee]
c/o Equifax Inc.                           c/o Certegy Inc.
1550 Peachtree Street
Atlanta, Georgia 30309                     ------------------------------------
Attn:  Kent E. Mast, General Counsel
                                           ------------------------------------
                                           Attn: Bruce S. Richards,
                                                 General Counsel

                                       10
<PAGE>

                                  Exhibit "E"
                                (Page 11 of 1)

                                       11