<PAGE>   1




                              TAX SHARING AGREEMENT

                  This TAX SHARING AGREEMENT ("Agreement") is made effective as
of January 1, 1999 between HNC Software Inc. ("HNC"), a Delaware corporation, on
behalf of itself, the Affiliated Group (as defined below) and the HNC Subgroup
(as defined below), on the one hand, and Retek Inc. ("Retek"), a Delaware
corporation, on behalf of Retek and the Retek Subgroup (as defined below), on
the other hand. Capitalized terms used herein shall have the meanings assigned
to them in Section 1 below.

                                    RECITALS

                  WHEREAS, HNC is the common parent corporation of an Affiliated
Group of corporations (as defined in Section 1504(a) of the Code) which includes
Retek;

                  WHEREAS, the Affiliated Group files consolidated federal
income Tax returns under Section 1501 of the Code, so that the Tax liability of
the Affiliated Group is determined under Section 1502 of the Code and the
Regulations thereunder by consolidating the income, expenses, gains, losses and
credits of all of the members of the Affiliated Group;

                  WHEREAS, HNC files state Combined Returns on behalf of itself
and other members of the Affiliated Group;

                  WHEREAS, it is the intent and desire of HNC, on behalf of
itself and its present and future subsidiaries other than Retek, RIS (as defined
below) and Retek's and RIS' present and future subsidiaries (collectively, the
"HNC Subgroup"), and Retek, on behalf of itself, RIS and Retek's and RIS'
present and future subsidiaries (collectively, the "Retek Subgroup") to provide
for the allocation and apportionment between the HNC Subgroup and the Retek
Subgroup of responsibilities, liabilities, and benefits relating to Taxes paid
or payable by the Affiliated Group, the HNC Subgroup, the Retek Subgroup or any
member of any such group;

                  WHEREAS, HNC's Board of Directors has determined that it is in
the best interest of HNC and its stockholders to separate the business of Retek
and Retek Information Systems, Inc. a Delaware corporation ("RIS") from HNC's
other operations in accordance with the series of related transactions set forth
in the Separation Agreement (the "Separation");



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                  WHEREAS, the Boards of Directors of HNC and Retek have
determined that it is appropriate and desirable that Retek issue and sell shares
of its common stock in an initial public offering registered under the
Securities Act of 1933, as amended (the "Initial Public Offering"); and

                  WHEREAS, HNC's current intention is that, after the closing of
the Initial Public Offering, HNC may in its sole discretion elect to distribute
pro rata to HNC's stockholders, as a dividend, the remaining shares of common
stock of Retek which it holds after the closing of the Initial Public Offering
(the "Distribution") subject to the terms, conditions and covenants set forth in
the Separation Agreement.

                                    AGREEMENT

                  NOW THEREFORE, in consideration of the mutual covenants and
promises contained herein, the parties agree as follows:

1.       DEFINITIONS

         1.1 "Adjustment" means an adjustment determined on an issue-by-issue or
transaction-by-transaction basis, as appropriate, made or proposed by a Taxing
Authority with respect to any amount reflected or required to be reflected on
any Return relating to such Tax.

         1.2 "Affiliated Group" means HNC, Retek and all other corporations
which may now or from time to time hereafter be eligible or required to be
included in a Consolidated Group Return with HNC as the common parent
corporation.

         1.3 "After Tax Basis" in reference to an indemnity payment under
Section 5.3 shall mean an amount that, after (i) subtraction of the aggregate
additional Taxes incurred or to be incurred by the party receiving the indemnity
payment as a result of the receipt of such payment and (ii) addition of the tax
benefit to the party receiving the indemnity payment on account of the
Adjustment to which such indemnity payment relates, is equal to the amount of
the Tax Adjustment. "After-Tax Basis" in reference to a benefit payment under
Section 5.3 shall mean an amount that, after (i) addition of the aggregate
additional Taxes incurred or to be incurred by the party making the benefit
payment on account of the Tax benefit to which such benefit payment relates and
(ii) subtraction of the Tax benefit to the party making the benefit payment as a
result of the making of such payment, is equal to the amount of the Tax benefit.
For purpose of determining such additional Taxes incurred or to be incurred and
such Tax benefit, the following assumptions will be used: (a) in the case of any
income Tax, the highest marginal Tax rate or, in

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the case of any other Tax, the highest applicable Tax rate, in each case in
effect with respect to that Tax for the Taxable period or any portion of the
Taxable period to which the indemnity payment or benefit payment relates; and
(b) such determination shall be made without regard to whether any actual
additional Taxes or Tax benefit will in fact be realized with respect to the
Return to which such payment relates.

         1.4 "Carryforward Tax Attribute" means a deductible or creditable
consolidated Federal tax attribute, including, but not limited to, (i) a
consolidated net operating loss, a consolidated net capital loss, a consolidated
unused foreign investment credit, a consolidated unused foreign tax credit, or a
consolidated excess charitable contribution (see Section 1.1502-79 of the
Regulations), and (ii) the consolidated minimum tax credit, or other
consolidated general business credits, that can be carried forward from one tax
period to subsequent tax periods.

         1.5 "Code" means the U.S. Internal Revenue Code of 1986, as amended.

         1.6 "Combined Return" means the Return of state income or franchise Tax
filed by a group of controlled corporations on a unitary basis as opposed to a
separate company basis.

         1.7 "Consolidated Group Return" means, with respect to any Consolidated
Return Year, the federal income Tax return of the Affiliated Group for such
Consolidated Return Year.

         1.8  "Consolidated Period" means that period of time during which Retek
is a member of the Affiliated Group.

         1.9  "Consolidated Return Date" means each date upon which the
Consolidated Group Return is filed.

         1.10 "Consolidated Return Year" means any Taxable year or period during
which HNC owns outstanding stock of Retek in such amounts and having such
characteristics as shall meet the requirements of Section 1504(a)(1) of the
Code.

         1.11 "Distribution Date" means the date on which the Distribution
occurs.

         1.12 "Effective Date" means January 1, 1999.

         1.13 "Estimated Payment Date" means each date occurring during any
Consolidated Return Year upon which the Consolidated Group is required to make a
payment of estimated Tax, whether or not such a payment is due, for such
Consolidated Return Year.

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         1.14 "Extension Payment Date" means, with respect to any Consolidated
Return Year, any date upon which the Affiliated Group shall be required to make
a payment of federal income Taxes in connection with any request by HNC, on
behalf of the Affiliated Group, for an extension of the date upon which it would
have been required, absent such extension, to file its federal income Tax return
for such Consolidated Return Year.

         1.15 "Final Determination" means (a) a decision, judgment, decree or
other order by any court of competent jurisdiction, which has become final and
is either no longer subject to appeal or for which a determination not to appeal
has been made; (b) a closing agreement made under Section 7121 of the Code or
any comparable foreign, state, local, municipal or other Taxing statute; (c) a
final disposition by any Taxing Authority of a claim for refund; or (d) any
other written agreement relating to an Adjustment to which any Taxing Authority
is a party the execution of which is final and prohibits such Taxing Authority
from seeking any further legal or administrative remedies with respect to such
Adjustment.

         1.16 "Group Refund Claim" means any claim filed by HNC on behalf of the
Affiliated Group for a refund of federal income Taxes or on behalf of the
Unitary Group for a refund of state income Taxes.

         1.17 "HNC Tax Adjustment" shall mean, with respect to any Taxable
period or portion of a Taxable period, and as computed separately with respect
to each Tax, the net increase in each such Tax equal to the sum of all Tax
Adjustments made pursuant to a Final Determination with respect to each such Tax
for each such Taxable period or portion of a Taxable period that are
attributable to the income, assets and/or business of any member of the HNC
Subgroup; provided, however, that any Tax Adjustment comprising a Restructuring
Adjustment shall not be considered in determining the amount of any HNC Tax
Adjustment.

         1.18 "HNC Tax Benefit" shall mean, with respect to any Taxable period
or portion of a Taxable period, and as computed separately with respect to each
Tax, the net decrease in each such Tax equal to the sum of all Tax Adjustments
made pursuant to a Final Determination with respect to each such Tax for each
such Taxable period or portion of a Taxable period that are attributable to the
income, assets and/or business of any member of the HNC Subgroup; provided,
however, that any Tax Adjustment comprising a Restructuring Adjustment shall not
be considered in determining the amount of any HNC Tax Benefit.

         1.19 "IRS" means the United States Internal Revenue Service.

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         1.20 "Person" means an individual, a general or limited partnership, a
corporation, a trust, a joint venture, an unincorporated organization, a limited
liability entity, or any other entity regardless of the type or nature thereof.

         1.21 "Regulations" means the Regulations issued by the Secretary of the
Treasury interpreting the Code.

         1.22 "Restructuring Adjustment" shall mean, with respect to any Taxable
period or portion of a Taxable period, and as computed separately with respect
to each Tax, the net increase or decrease in each such Tax, as the case may be,
equal to the sum of all Tax Adjustments made pursuant to a Final Determination
with respect to each such Tax for each Taxable period or portion of a Taxable
period that are attributable to, or are a result of, the Separation, the Initial
Public Offering or the Distribution.

         1.23 "Retek Tax Adjustment" shall mean, with respect to any Taxable
period or portion of a Taxable period, and as computed separately with respect
to each Tax, the net increase in each such Tax equal to the sum of all Tax
Adjustments made pursuant to a Final Determination with respect to each such Tax
for each such Taxable period or portion of a Taxable period that are
attributable to the income, assets and/or business of any member of the Retek
Subgroup; provided, however, that any Tax Adjustment comprising a Restructuring
Adjustment shall not be considered in determining the amount of any Retek Tax
Adjustment.

         1.24 "Retek Tax Benefit" shall mean, with respect to any Taxable period
or portion of a Taxable period, and as computed separately with respect to each
Tax, the net decrease in each such Tax equal to the sum of all Tax Adjustments
made pursuant to a Final Determination with respect to each such Tax for each
such Taxable period or portion of a Taxable period that are attributable to the
income, assets and/or business of any member of the Retek Subgroup; provided,
however, that any Tax Adjustment comprising a Restructuring Adjustment shall not
be considered in determining the amount of any Retek Tax Benefit.

         1.25 "Return" means any return, report, form or similar statement or
document (including, without limitation, any related or supporting information
or schedule attached thereto and any information return, claim for, amended
return and declaration of estimated Tax) that has been or is required to be
filed with any Taxing Authority or that has been or is required to be furnished
to any Taxing Authority in connection with the determination, assessment or
collection of any Taxes or the administration of any laws, regulations or
administrative requirements relating to any Taxes.

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         1.26 "Separate Return Period" means that period of time during which
Retek is not a member of the Affiliated Group.

         1.27 "Separation Agreement" means the Separation Agreement, dated as of
November 23, 1999 by and among HNC, Retek and RIS.

         1.28 "Tax" (and, with correlative meanings, "Taxes" and "Taxable")
means, without limitation, and as determined on a jurisdiction-by-jurisdiction
basis, each foreign or U.S. federal, state, local or municipal income,
alternative or add-on minimum, gross receipts, sales, use, ad valorem, transfer,
franchise, profits, license, withholding, payroll, employment, excise,
severance, stamp, occupation, premium, property, value added or any other tax,
custom, tariff, impost, levy, duty, governmental fee or other like assessment or
charge of any kind whatsoever, together with any interest, or penalty, addition
to tax or additional amount related thereto, imposed by any Taxing Authority.

         1.29 "Tax Adjustment" shall mean the deemed increase or decrease in a
Tax, determined on an issue-by-issue or transaction-by-transaction basis, as
appropriate, and using the assumptions set forth in the next sentence, resulting
from an adjustment made or proposed by a Taxing Authority with respect to any
amount reflected or required to be reflected on any Return relating to such Tax.
For purpose of determining such deemed increase or decrease in a Tax, the
following assumptions will be used: (a) in the case of any Income Tax, the
highest marginal Tax rate or, in the case of any other Tax, the highest
applicable Tax rate, in each case in effect with respect to that Tax for the
Taxable period or any portion of the Taxable period to which the adjustment
relates; and (b) such determination shall be made without regard to whether any
actual increase or decrease in such Tax will in fact be realized with respect to
the Return to which such adjustment relates.

         1.30 "Taxing Authority" means any governmental authority or any
subdivision, agency, commission or authority thereof, or any quasi-governmental
or private body having jurisdiction over the assessment, determination,
collection or other imposition of Taxes.

         1.31 "Tax Contest" means, without limitation, any audit, examination,
claim, suit, action or other proceeding relating to Taxes in which an Adjustment
to Taxes may be proposed, collected or assessed and in respect of which an
indemnity payment, reimbursement or other payment may be sought under this
Agreement.

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         1.32 "Unitary Group" means HNC, Retek and all other corporations which
may now or from time to time hereafter be eligible or required to be included in
a Combined Return with HNC.

2.       FILING OF CONSOLIDATED RETURNS

         2.1 Consent to File. Retek hereby consents to the filing of
Consolidated Group Returns by HNC on behalf of the Affiliated Group, including
Retek and the Retek Subgroup, for each Consolidated Return Year, and to any
applications for extensions of time to file such Returns which HNC in its sole
judgment shall make to the IRS. Retek hereby consents to the filing of Combined
Returns by HNC on behalf of the Unitary Group, including Retek and the Retek
Subgroup, for each year (or portion thereof) in which HNC owns, directly or
indirectly, 50% or more of the equity of Retek, and to any applications for
extensions of time to file such Returns which application HNC in its sole
judgment shall make to the applicable Taxing Authorities.

         2.2 Responsibility for Preparing and Filing. HNC shall be entitled to
prepare and file and shall be responsible for the preparation and filing, of the
Consolidated Group Returns and any Combined Returns, including but not limited
to determining all Tax Return positions, paying estimated taxes and other
consolidated Taxes and making all federal and state tax elections for the
Affiliated Group and/or the Unitary Group and each member of such groups;
provided, however, that at least 10 days prior to filing any Consolidated Group
Return, HNC shall provide Retek the opportunity to review the portion of such
draft Consolidated Group Return that reflects the income and operations of the
Retek Subgroup. Retek shall communicate its comments, if any, to HNC at least 5
days prior to the due date, including extensions, for filing such Tax return.

         2.3 Further Action. Retek agrees, at HNC's request, to furnish to HNC
and/or any Taxing Authority any and all information and to execute all elections
and other documents which may be necessary or appropriate, in the judgment of
HNC, to evidence Retek's consent or to facilitate the preparing and filing of
such Returns and applications for extension of time to file such Returns. This
obligation applies to all Tax Returns for any Consolidated Return Year even if
such Return is filed after Retek is no longer a member of the Affiliated Group.

3.       ALLOCATION AND PAYMENT OF LIABILITIES FOR TAXES

         3.1 Federal Income Taxes for Periods Commencing on and after the
Effective Date. HNC (on behalf of itself and other members of the HNC Subgroup)
and Retek (on behalf of itself and other members of the Retek Subgroup) agree to
determine and allocate the federal income Tax liability of the Affiliated Group
among themselves in the following manner:

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                  (a) For each Taxable period commencing on or after the
Effective Date in which Retek and/or any other member of the Retek Subgroup is
included in the Affiliated Group, the Retek Subgroup shall be allocated, and
Retek shall pay to HNC as provided in this Section 3 and in Section 4 an amount
equal to, the federal income Tax liability, if any (including any alternative
minimum Tax), of Retek and/or the other member(s) of the Retek Subgroup included
in the Affiliated Group, as determined by HNC in accordance with the methods set
forth in this Section 3.1. Such federal Tax liability shall equal the
hypothetical separate return Tax liability of the Retek Subgroup, as determined
in accordance with the provisions of Treasury Regulations Section
1.1552-1(a)(2)(ii) (treating references to a "member" therein as references to
the Retek Subgroup, and including the adjustments under clauses (a)-(i) thereof)
as if the Retek Subgroup had filed a separate consolidated federal income Tax
Return. If the Retek Subgroup's federal Tax liability as so determined is zero,
then HNC shall pay to Retek an amount equal to the excess, if any, of the HNC
Subgroup's federal income Tax liability, determined as if the HNC Subgroup had
filed a separate consolidated federal income Tax Return for such Taxable period
or portion thereof (and any Taxable year of the HNC Subgroup to which a net
operating loss or other Tax item of the Retek Subgroup is carried) under the
same principles as set forth in the preceding sentence, over the actual federal
income Tax liability of the Affiliated Group for such Taxable period or portion
thereof (or such year to which such item is carried).

                  (b) For purposes of determining and allocating Tax liabilities
and payment obligations for Tax periods commencing on or after the Effective
Date, (i) the Retek Subgroup's federal and state income Tax liability will be
computed by HNC in a manner consistent with HNC's policies and procedures for
accounting for income taxes for financial statement purposes; (ii) the benefit
of the graduated Tax rates provided under Section 11 of the Code and any
alternative minimum Tax exemption amount under Section 55 of the Code shall be
allocated to the Retek Subgroup in proportion to the ratio of the Retek
Subgroup's federal Tax liability to the total federal Tax liability of the
Affiliated Group (computed without regard to such benefit); and (iii) items not
otherwise specifically addressed hereunder shall be allocated between the Retek
Subgroup and the HNC Subgroup by HNC in a manner that reasonably reflects the
provisions, purposes and intent of this Agreement.

                  (c) The Retek Subgroup's federal income Tax liability for the
Taxable year during which Retek ceases to be a member of the Affiliated Group
shall be determined in accordance with the provisions of Regulations Section
1.1502-76(b)(2) by closing the books of Retek and the other members of the Retek
Subgroup as of the end of the last day of the Consolidated Return Year and
taking into account only items accruing during the portion of the Taxable year
ending on such date in computing such liability. Items shall not be pro-rated in

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accordance with clauses (ii) or (iii) of Section 1.1502-76(b)(2) of the
Regulations except to the extent HNC in its discretion determines that it is
impracticable to allocate particular items in accordance with the preceding
sentence.

                  (d) The parties acknowledge that the allocation of federal Tax
liability provided for by this Section 3.1 is for purposes of determining the
parties' actual payment obligations to each other with respect to Taxes of the
Affiliated Group for the Consolidated Return Year and not for purposes of
computing earnings and profits pursuant to Section 1552 of the Code. HNC and
Retek each recognizes that such allocation may differ from the allocation
provided by Section 1552 for earnings and profits purposes.

                  (e) It is acknowledged that allocation of the consolidated
federal income Tax liability for the Affiliated Group under Section 1.1552-1(a)
of the Regulations shall (in accordance with Section 1.1552-1(b)(2) of the
Regulations), in the amount allocated to each member of the HNC Subgroup and the
Retek Subgroup, decrease the earnings and profits of such member and be treated
as a liability of such member for such amount. It is further acknowledged that
if allocations of federal income Tax liability in accordance with Section 3.1 of
this Agreement differ from the allocations in accordance with Section
1.1552-1(a)(1), HNC and Retek hereby agree that such differences will not create
liabilities and receivables, but rather will be regarded as distributions with
respect to stock, contributions to capital, or combinations thereof, as
applicable.

         3.2      State Income and Franchise Taxes for Periods Commencing on or
after the Effective Date.

                  (a) For each Taxable period commencing on or after the
Effective Date for which Retek and/or any other member of the Retek Subgroup is
included in any Combined Return filed by the Unitary Group, the Retek Subgroup
shall be allocated, and Retek shall pay to HNC in accordance with this Section
3.2 and Section 4 an amount equal to, the state income Tax liability of Retek
and/or such other Retek Subgroup members that are so included, as determined
under this Section 3.2. Such state income Tax liability shall equal the
hypothetical state income Tax liability of the Retek Subgroup members so
included, computed as if they filed a Combined Return (or if only one such
member is so included, a separate state income or franchise Tax return )
including only such included member(s). To the extent that the same or analogous
federal consolidated reporting principles as are referred to in Section 3.1
apply for purposes of filing such Combined Return(s), then such principles shall
also apply for purposes of determining the Retek Subgroup's state Tax liability
in respect of any Combined Return of the Unitary Group. If the state income Tax
liability of the Retek Subgroup as so determined is zero, then HNC shall pay to

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Retek an amount equal to the excess, if any, of the HNC Subgroup's state income
Tax liability, determined as if the HNC Subgroup had filed a separate Combined
Return not including any Retek Subgroup members, over the actual state income
Tax liability of the Unitary Group. HNC shall have the discretion to determine
each subgroup's liability for Taxes under this Section 3.2(a) in any manner that
is reasonable in light of the applicable state and local Tax reporting
principles and the purposes and intent of this Agreement.

                  (b) Retek shall be responsible for payment of any state Taxes
due from it or any members of the Retek Subgroup, and HNC shall be responsible
for payment of any state Taxes due from HNC or any member of the HNC Subgroup,
in connection with state income or franchise Returns that are not Combined
Returns. Retek shall be responsible for preparing and filing any state Tax
returns, other than Combined Returns, for itself and the Retek Subgroup.

                  (c) To the extent that HNC pays any Tax on behalf of any
member of the Retek Subgroup, Retek shall reimburse HNC with ten (10) days of
receipt of an invoice requesting payment thereof.

4.       ESTIMATED PAYMENTS OF TAX SHARING LIABILITY

         4.1 Hypothetical Tax Computation and Payment Thereof. At least three
(3) days prior to each Estimated Payment Date of each Consolidated Return Year,
HNC shall deliver to Retek hypothetical computations of estimated Tax for Retek
reflecting the amounts, if any, of the estimated payment of federal and/or state
income Taxes and franchise Taxes for such Consolidated Return Year, as
applicable, which Retek would have been required to pay on such Estimated
Payment Date if it were not included in the Affiliated Group or Unitary Group
(calculated in accordance with Article 3). Retek shall pay to HNC, on such
Estimated Payment Date, the amounts reflected as owing in such hypothetical
computations.

         4.2 Extension Payments. Notwithstanding Section 4.1, if HNC shall
request an extension of time to file the Consolidated Group Return and/or the
Combined Return for any Consolidated Return Year, HNC shall compute the
hypothetical amounts of the federal or state income Tax payment, as applicable,
which would have been payable by Retek on such Extension Payment Date had Retek
requested such an extension and had Retek not been included in the Affiliated
Group or Unitary Group during such Consolidated Return Year (calculated in
accordance with Article 3). Retek shall pay to HNC, on such Extension Payment
Date, the amounts computed by HNC.

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         4.3 Waiver. HNC, in its sole discretion, may waive on an annual basis
the requirement for Retek to make the estimated Tax payments as described in
this Section 4.

         4.4 Date Consolidated Group and/or Combined Return Filed. HNC shall
compute the hypothetical amount of the federal, state and/or franchise Tax which
would have been payable by Retek on such actual filing date had Retek not been
included in the Affiliated Group or Unitary Group during such Consolidated
Return Year (calculated in accordance with Section 3). Retek shall pay to HNC
the amount computed, less the aggregate of any amounts previously paid on each
Estimated Payment Date and Extension Payment Date pursuant to this Section 4.
Retek shall pay HNC the computed amount owed within ten (10) days of the later
of (i) the date on which the Tax Return is filed, or (ii) receipt of an invoice
showing the computed amount owed. If the aggregate amounts paid by Retek on the
Estimated Payment Dates and Extension Payment Dates for a Consolidated Return
Year exceed the computed hypothetical federal, state and/or franchise Tax
payable by Retek, then HNC shall refund to Retek any such excess amount within
ten (10) days of filing the applicable Tax Return.

5.       DISPUTES WITH TAXING AUTHORITIES

         5.1 Confirmation of Authority. In the event of a Tax Contest with the
IRS or any other Taxing Authority concerning the amount of any Tax liability of
or refund due to the Affiliated Group or any member thereof for any Consolidated
Return Year, and in connection with every Group Refund Claim or other claim for
refund of Tax for any Consolidated Return Year, Retek hereby expressly confirms,
with respect to federal income Tax liability, the authority granted to HNC in
Regulations Section 1.1502-77 (and in any successor provision thereto) of the
Regulations to act on behalf of Retek and the Retek Subgroup notwithstanding
that Retek may be liable for additional tax or for additional payments to HNC.
With respect to such federal Taxes and all other Taxes, Retek hereby expressly
and irrevocably appoints HNC to be its sole agent and expressly relinquishes any
rights it may have to act for or represent itself in any manner in any such Tax
Contest or with respect to any such Group Refund Claim related to the time
period in which Retek and/or any member of the Retek Subgroup is a member of the
Affiliated Group. Retek hereby authorizes HNC and its representatives to pursue
such Tax Contest, Group Refund Claim, or other claim for refund of Tax either
administratively or by court action. Retek hereby irrevocably agrees that HNC
shall have the exclusive right, on behalf of Retek and the Retek Subgroup, to
make any and all decisions to pursue, settle, or appeal any Tax Contest, Group
Refund Claim or other claim for refund of Tax, and to control all administrative
and court proceedings and any and all negotiations and settlements related
thereto. Retek hereby expressly consents to HNC entering into settlements on its
behalf and on behalf of the Retek Subgroup, as

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HNC deems appropriate in its sole discretion, exercised in good faith; provided,
however, that prior to settling an issue that would give rise to Tax Adjustment
for which Retek or a member of the Retek Subgroup would be liable under this
Agreement, Retek shall have the right and opportunity to review such settlement.
HNC may, in its sole discretion, exercised in good faith, accept or reject any
suggestions made by Retek with respect to such settlement; provided, however,
that HNC shall not reject any suggestion made by Retek if to do so would be
unreasonable. Retek may assist in the defense of audit issues arising from its
operations, at its own expense, subject to the direction and control of HNC.
Retek shall reimburse HNC for all reasonable out-of pocket expenses (including,
with limitation, legal, consulting and accounting fees) in the course of a Tax
Contest regarding an item of the Retek Subgroup for any Taxable period during
which the Retek Subgroup was a member of the Affiliated Group to the extent such
expenses are reasonably attributable to such Tax Contest.

         5.2 Agreement to Cooperate. Retek agrees to cooperate and cause the
Retek Subgroup to cooperate fully and in a timely manner with HNC in connection
with the preparation of Tax Returns, the pursuit of any Group Refund Claim or
other claim for refund of Taxes or the conduct of any Tax Contest for any
Consolidated Return Year, at Retek's own expense by taking any and all action
that may be necessary or helpful, as requested by HNC, including (without
limitation) furnishing to HNC access to and copies of all records and documents
and making personnel available for interviews and testimony. This agreement to
cooperate extends beyond the date after which Retek is no longer a member of the
Affiliated Group.

         5.3      Adjustments.

                  (a) In the event there is an Adjustment, made pursuant to a
Final Determination, of an item of income, gain, loss, deduction, or credit with
respect to any Return of any member of the Affiliated Group for any Taxable
period during which Retek and/or any other member of the Retek Subgroup is or
was a member of the Affiliated Group:

                           (i)      Retek shall be liable for, and shall
indemnify and hold harmless, as appropriate, any member of the HNC Subgroup, on
an After Tax Basis against any and all Retek Tax Adjustments;

                           (ii)     Retek shall be entitled to any Retek Tax
Benefits on an After Tax Basis;

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                           (iii)    HNC shall be liable for, and shall indemnify
and hold harmless, as appropriate, any member of the Retek Subgroup on an After
Tax Basis against any and all HNC Tax Adjustments; and

                           (iv)     HNC shall be entitled to receive on an After
Tax Basis the amount of any HNC Tax Benefits.

                  (b) HNC and Retek shall share the amount of any Tax
Adjustment, other than a Restructuring Adjustment, if, and to the extent, each
party is liable for and/or has an obligation to make, or has the right to
receive, as the case may be, any indemnity payment, or other payment with
respect to such Tax Adjustment under Section 5.3(a), in proportion to the
amounts of the underlying Adjustments giving rise to such Tax Adjustment
attributable to the HNC Subgroup and the Retek Subgroup respectively.

                  (c) HNC and Retek shall share the amount of any Tax
Adjustment, other than a Restructuring Adjustment, not covered by Section 5.3(a)
or Section 5.3(b) above in proportion to the amounts of the underlying
Adjustments related to such Tax Adjustment attributable to the HNC Subgroup and
the Retek Subgroup respectively.

                  (d) Notwithstanding any other provision of this Agreement,
Retek shall be liable for, and shall indemnify and hold harmless, as
appropriate, any member of the HNC Subgroup on an After Tax Basis against any
and all Restructuring Adjustments arising out of, or in connection with, the
Separation or the Initial Public Offering.

                  (e) The indemnification provisions of this Agreement shall
supplement the indemnification provisions of the Separation Agreement. In
particular, the Separation Agreement provides for indemnification with respect
to any Restructuring Adjustment arising out of, or in connection with, the
Distribution. To the extent there is any conflict between the indemnification
provisions of this Agreement and the indemnification provisions of the
Separation Agreement, the indemnification provisions of the Separation Agreement
shall control.

                  (f) Indemnity payments and other amounts required to be paid
under Sections 5.3(a), 5.3(b) 5.3(c) and 5.3(d) shall be paid within 60 days of
the date of such Final Determination. HNC shall provide Retek with prompt
written notice of each such Final Determination.

                                       13

<PAGE>   14



6.       DISTRIBUTION TAXES AND TAX ATTRIBUTE CARRYOVERS

         6.1 Taxes Relating to the Distribution. Notwithstanding any statement
herein to the contrary, any Taxes relating to or arising out of the Distribution
shall be governed by Article V of the Separation Agreement.

         6.2 Carryforward Tax Attributes. The Carryforward Tax Attributes
available to Retek for Separate Return Periods will be determined by allocating
the Carryforward Tax Attributes of the HNC Group to tax periods beginning after
the Distribution Date among the HNC Subgroup and Retek Subgroup as described
below:

                  (a) Federal Tax Attributes. Any Carryforward Tax Attributes
allocable to Retek or a member of the Retek Subgroup shall remain with Retek or
such member. The portion, if any, of any HNC Group consolidated unused foreign
tax credit which is allocable to Retek shall be determined separately with
respect to each of the items of income listed in Section 904(d) of the Code.

                  (b) State or Local Income Tax Attributes. No tax attributes
arising from state or local Income Tax Returns shall be allocated to Retek,
unless under the provisions of applicable state law or state regulations such
tax attributes are expressly required to be allocated to Retek.

         6.3 Carryback Items from Separate Return Tax Periods. With respect to
carrybacks of Retek or net operating losses, net capital losses, unused tax
credits and other deductible or creditable Tax attributes to a Consolidated
Period from a Separate Return Period which would be permitted under the Code and
the Regulations (or state law or state regulations), Retek shall make an
irrevocable election under Regulations Section 1.1502-21(b)(3)(i) (or comparable
state law or state regulations), to relinquish any carryback period which would
include the Consolidated Period. In cases where Retek cannot relinquish the
carryback period or, if the parties otherwise agree, HNC shall cooperate with
Retek in seeking Tax refunds from the appropriate Taxing Authority, at Retek's
expense, and Retek shall be entitled to such refund, including interest paid by
the Taxing Authority in connection with such refund; provided however, that
Retek shall indemnify and hold HNC harmless from and against any and all
collateral Tax consequences, including interest, resulting from or caused by the
carryback of deductible or creditable Tax attributes by Retek from a Separate
Return Period to a Consolidated Period, including but not limited to, Tax
attributes of HNC that expire unused (including Tax attributes that expire
during a Tax period subsequent to the Tax period during which the Retek Tax
attribute carried back was generated) and which would have been used but for
Retek's carryback. The amount of such indemnity shall be limited to the actual
Tax benefits to which HNC would

                                       14

<PAGE>   15



have been entitled in the absence of the carryback of the deductible or
creditable Tax attribute of Retek. Retek shall have the right to review the
collateral Tax consequences being indemnified. The amount of the refund due to
Retek from HNC shall be reduced and offset by the amount of the indemnification,
if any.

         6.4      Post-Consolidated Period Taxes.

                  (a) HNC shall indemnify and hold Retek and the Retek Subgroup
harmless for any Taxes relating to Tax Returns of HNC or the HNC Subgroup for
any Separate Return Period.

                  (b) Retek shall indemnify and hold HNC and the HNC Subgroup
harmless for any Taxes relating to Tax Returns of Retek or the Retek Subgroup
for any Separate Return Period.

7.       PRIORITY OF AGREEMENT

         7.1 Fixing of Liability. The provisions of this Agreement shall
determine and fix the liability of the parties to each other as to the matters
provided for herein, regardless of how the payments made pursuant hereto are
treated for Tax purposes.

8.       OTHER GROUP MEMBERS

         8.1 Agreements. HNC and Retek recognize that other corporations are now
or may from time to time hereafter become members of the Affiliated Group and it
may become appropriate to adopt different or additional methods of sharing
Taxes. Retek, on behalf of itself and the Retek Subgroup, hereby authorizes HNC
to enter into the same, similar or different supplemental, conflicting or
replacement Tax sharing agreements on behalf of the Affiliated Group (including
Retek and the Retek Subgroup) with any corporation which is now or may hereafter
become a member of the Affiliated Group.

9.       RECORDS

         9.1 Retention by HNC. HNC shall, until the end of the applicable
statute of limitations for each Tax year (giving effect to any extensions
thereof), retain all material, including but not limited to, returns, supporting
schedules, workpapers, correspondence, and other documents relating to the
Consolidated Group Returns and Combined Returns filed for a Taxable year during
which Retek is a member of the Affiliated Group and shall make such items
available to Retek for inspection or copying (at Retek's expense) during HNC's
regular business hours.

                                       15

<PAGE>   16



         9.2 Retention by Retek. Retek shall, until the end of the applicable
statute of limitations for each Tax year (giving effect to any extensions
thereof), retain all material, supporting schedules, workpapers, correspondence,
and other documents relating to Consolidated Group Returns and Combined Returns
filed for a Taxable year during which Retek is a member of the Affiliated Group
and shall make such items available to HNC for inspection or copying (at HNC's
expense) during Retek's regular business hours.

10.      TERM AND TERMINATION

         10.1 Term. This Agreement shall be effective as of January 1, 1999, and
shall apply to and govern all subsequent Taxable periods, unless the parties
hereto each agree in writing to terminate this Agreement. Notwithstanding any
such termination, this Agreement shall continue in effect with respect to any
payment due from one party to the other with respect to any Taxable period
occurring prior to the effective date of the termination of this Agreement.

11.      MISCELLANEOUS

         11.1 Governing Law. The internal laws of the State of California
(irrespective of its choice of law principles) will govern the validity of this
Agreement, the construction of its terms and the interpretation and enforcement
of the rights and duties of the parties hereto.

         11.2 Assignment; Binding Upon Successors and Assigns. Retek may not
assign, whether voluntarily or by operation of law, any of its rights or
obligations hereunder without the prior written consent of HNC, which consent
may be withheld in its sole discretion. HNC may assign its rights (but not its
obligations) under this Agreement without the consent of Retek; provided,
however, that the rights and obligations of HNC may be assigned, without the
consent of Retek, pursuant to a merger, exchange, recapitalization or other
reorganization to which HNC is a party or by operation of law. This Agreement
will be binding upon and inure to the benefit of the parties hereto and their
respective successors and permitted assigns. Any member corporation which leaves
the Affiliated Group shall be bound by this Agreement.

         11.3 Severability. If any provision of this Agreement, or the
application thereof, will for any reason and to any extent be invalid or
unenforceable, the remainder of this Agreement and application of such provision
to other persons or circumstances will be interpreted so as reasonably to effect
the intent of the parties hereto. The parties further agree to replace such void
or unenforceable provision of this Agreement with a valid and enforceable
provision that will achieve, to the greatest extent possible, the economic,
business, Tax and other purposes of the void or unenforceable provision.

                                       16

<PAGE>   17



         11.4 Counterparts. This Agreement may be executed in any number of
counterparts, each of which will be an original as regards any party whose
signature appears thereon and all of which together will constitute one and the
same instrument. This Agreement will become binding when one or more
counterparts hereof, individually or taken together, will bear the signatures of
all the parties reflected hereon as signatories.

         11.5 Other Remedies. Except as otherwise provided herein, any and all
remedies herein expressly conferred upon a party will be deemed cumulative with
and not exclusive of any other remedy conferred hereby or by law on such party,
and the exercise of any one remedy will not preclude the exercise of any other.

         11.6 Amendment and Waivers. Any term or provision of this Agreement may
be amended, and the observance of any term of this Agreement may be waived
(either generally or in a particular instance and either retroactively or
prospectively) only by a writing signed by the party to be bound thereby. The
waiver by a party of any breach hereof or default in the performance hereof will
not be deemed to constitute a waiver of any other default or any succeeding
breach or default. Failure by either party, at any time, to require performance
by the other party or to claim a breach of any provision of this Agreement shall
not be construed as a waiver of any right accruing under this Agreement, nor
shall it affect any subsequent breach or the effectiveness of this Agreement or
any part hereof, or prejudice either party with respect to any subsequent
action.

         11.7 Expenses. Unless otherwise provided, all fees and expenses
incurred in connection with this Agreement will be paid by the party incurring
such fees or expenses.

         11.8 Attorneys' Fees. Should suit be brought to enforce or interpret
any part of this Agreement, the prevailing party will be entitled to recover, as
an element of the costs of suit and not as damages, reasonable attorneys' fees
to be fixed by the court (including, without limitation, costs, expenses and
fees on any appeal). The prevailing party will be entitled to recover its costs
of suit, regardless of whether such suit proceeds to final judgment.

         11.9 Dispute Resolution. The parties shall attempt in good faith to
resolve any dispute arising out of or relating to this Agreement and shall
attempt in good faith to negotiate a settlement of any dispute pursuant to the
following process:

                  (a) Any party having a dispute or claim shall give the other
party written notice stating the nature of the dispute in reasonable detail.
Within ten (10) business days after delivery of the notice, the receiving party
shall submit to the other a written response also in reasonable

                                       17

<PAGE>   18



detail. Within five (5) business days after delivery of the written response the
Chief Financial Officer (or other individual who has authority to settle the
controversy and who has direct responsibility for administration of the
relationships established pursuant to this Agreement) for each party shall meet
(in person or by telephone) at a mutually acceptable time and place (including
telephonic conference), and thereafter as often as they reasonably deem
necessary, to attempt to resolve the dispute. All reasonable requests for
information made by one party to the other shall be honored.

                  (b) If such matter has not been resolved within ten (10)
business days of the referral of the dispute to the Chief Financial Officers,
then the parties may pursue litigation or, if mutually agreed, alternative
dispute resolution mechanisms.

         11.10 Notices. All notices and other communications pursuant to this
Agreement shall be in writing and deemed to be sufficient if contained in a
written instrument and shall be deemed given if delivered personally,
telecopied, sent by nationally-recognized overnight courier or mailed by
registered or certified mail (return receipt requested), postage prepaid, to the
parties at the addresses indicated on the signature page of this Agreement (or
at such other address for a party as shall be specified by like notice). All
such notices and other communications shall be deemed to have been received (a)
in the case of personal delivery, on the date of such delivery, (b) in the case
of a telecopy, when the party receiving such copy shall have confirmed receipt
of the communication, (c) in the case of delivery by nationally-recognized
overnight courier, on the business day following dispatch, and (d) in the case
of mailing, on the tenth business day following such mailing. Failure of a party
to provide notice in a prescribed time period or in a timely manner shall not
constitute a waiver of the other party's obligation hereunder. Where notice is a
condition to payment, the obligation to make the payment shall not be waived,
forgiven or eliminated by virtue of a failure to give notice; however, the time
period in which an amount must be paid shall be measured from the date on which
notice is actually given.

         11.11 Representation by Counsel. Each of the parties hereto is
represented by separate counsel of its own choosing. Each of the parties hereto
has had an opportunity to ask questions of and receive advice from its counsel
regarding the terms and conditions of this Agreement. This Agreement has been
negotiated by the respective parties hereto and their attorneys and the language
hereof will not be construed for or against either party, notwithstanding that
as of the date hereof Retek is a wholly-owned subsidiary of HNC.

         11.12 Construction of Agreement. A reference to a Section will mean a
Section in this Agreement unless otherwise explicitly set forth. The titles and
headings herein are for reference

                                       18

<PAGE>   19



purposes only and will not in any manner limit the construction of this
Agreement which will be considered as a whole.

         11.13 Jurisdiction and Venue. The parties hereto irrevocably consent to
and agree that any litigation or other dispute resolution proceeding among the
parties relating to this Agreement will take place in San Diego County,
California. The parties hereby irrevocably consent to the personal jurisdiction
or and the venue in the state and federal court within such county.

         11.14 Further Assurances. Each party agrees to cooperate fully with the
other parties and to execute such further instruments, documents and agreements
and to give such further written assurances as may be reasonably requested by
any other party to evidence and reflect the transactions contemplated hereby and
to carry into effect the intents and purposes of this Agreement.

         11.15 Entire Agreement. This Agreement constitutes the entire
understanding and agreement of the parties hereto with respect to the subject
matter hereof and supersedes all prior and contemporaneous agreements or
understandings, inducements or conditions, express or implied, written or oral,
between the parties with respect hereto.

                                       19

<PAGE>   20
     IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
by their duly authorized officers.

HNC SOFTWARE INC.                      RETEK, INC.

on behalf of itself and the HNC        on behalf of itself and the Retek
Subgroup                               Subgroup


By:    /s/  R.V. Thomas                By:    /s/  Gregory A. Effertz
       ---------------------------            -------------------------------
Name:  R.V. Thomas                     Name:  Gregory A. Effertz
       ---------------------------            -------------------------------
Title: C.F.O.                          Title: V.P. Finance and Administration
       ---------------------------            -------------------------------


Address for Notice:                    Address for Notice:
-------------------                    -------------------

HNC Software Inc.                      Retek, Inc.
5935 Cornerstone Court West            Midwest Plaza
San Diego, CA 92121                    801 Nicollet Mall, 11th Floor
FAX: (858) 452-3220                    Minneapolis, MN 55402
                                       FAX: (612) 630-5641

Attention: Chief Financial Officer     Attention: Chief Financial Officer