<PAGE>   1
                                                                   EXHIBIT 10.21


                             TAX SHARING AGREEMENT,

                           DATED AS OF _________, 2001

                                  BY AND AMONG

                         REUTERS AMERICA HOLDINGS, INC.

                              INSTINET GROUP, LLC,

                          INSTINET GROUP INCORPORATED,

                                       AND

                         INSTINET GLOBAL HOLDINGS, INC.
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                                TABLE OF CONTENTS

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Section 1.  DEFINITIONS...............................................................      2

Section 2.  PREPARATION AND FILING OF TAX RETURNS.....................................      8

     2.1    IN GENERAL................................................................      8

     2.2    MANNER OF PREPARING AND FILING TAX RETURNS................................      8

Section 3.  PAYMENT OF TAXES TO TAX AUTHORITIES.......................................     10

     3.1    FEDERAL INCOME TAXES......................................................     10

     3.2    NON-FEDERAL COMBINED TAXES................................................     10

     3.3    NON-FEDERAL SEPARATE TAXES................................................     10

     3.4    OTHER FEDERAL TAXES.......................................................     10

Section 4.  ALLOCATION OF TAXES.......................................................     10

     4.1    INSTINET LIABILITY FOR FEDERAL INCOME TAXES AND NON-FEDERAL COMBINED TAXES     10

     4.2    INSTINET GROUP FEDERAL INCOME TAX LIABILITY...............................     10

     4.3    INSTINET GROUP COMBINED TAX LIABILITY.....................................     11

     4.4    COOPERATION...............................................................     11

     4.5    TAX SHARING INSTALLMENT PAYMENTS..........................................     12

     4.6    TAX SHARING TRUE-UP PAYMENTS..............................................     12

     4.7    REDETERMINATION AMOUNTS...................................................     13

     4.8    PAYMENT OF TAXES FOR POST-DECONSOLIDATION PERIODS.........................     13

Section 5.  TAX ATTRIBUTES............................................................     13

     5.1    ALLOCATION OF TAX ITEMS...................................................     13

     5.2    POST DECONSOLIDATION......................................................     14

Section 6.  ADDITIONAL OBLIGATIONS....................................................     14

     6.1    PROVISION OF INFORMATION AND MUTUAL COOPERATION...........................     14

     6.2    INDEMNIFICATION...........................................................     15

     6.3    TAX CONSEQUENCES OF PAYMENTS..............................................     15

     6.4    INTEREST..................................................................     17

Section 7.  AUDITS....................................................................     17

     7.1    IN GENERAL................................................................     17
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                                TABLE OF CONTENTS
                                   (CONTINUED)

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                                                                                          PAGE

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     7.2    NOTICE....................................................................     17

     7.3    PARTICIPATION RIGHTS......................................................     18

     7.4    SETTLEMENT................................................................     19

     7.5    AFFIRMATIVE CLAIMS........................................................     19

Section 8.  LIABILITY FOR RESTRUCTURING TAXES AND DECONSOLIDATION TAXES...............     20

Section 9.  MISCELLANEOUS.............................................................     21

     9.1    EFFECTIVENESS.............................................................     21

     9.2    NOTICES...................................................................     21

     9.3    CHANGES IN LAW............................................................     21

     9.4    SUCCESSORS AND ASSIGNS....................................................     21

     9.5    AUTHORIZATION, ETC........................................................     22

     9.6    COMPLETE AGREEMENT........................................................     22

     9.7    INTERPRETATION............................................................     22

     9.8    GOVERNING LAW.............................................................     22

     9.9    COUNTERPARTS..............................................................     22

     9.10   LEGAL ENFORCEABILITY......................................................     22

     9.11   NO THIRD PARTY BENEFICIARIES..............................................     22

     9.12   JURISDICTION; FORUM.......................................................     22

     9.13   AMENDMENT AND MODIFICATION................................................     23
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                             TAX SHARING AGREEMENT

                  TAX SHARING AGREEMENT (this "Agreement"), dated as of
February__, 2001, by and among Reuters America Holdings, Inc. ("Reuters"), a
Delaware corporation, Instinet Group, LLC, a Delaware limited liability company,
the successor entity to be formed by the conversion of Instinet Group LLC to a
Delaware corporation("Instinet Group Incorporated") and Instinet Global
Holdings, Inc., a Delaware corporation (Instinet Group, LLC, Instinet Group
Incorporated and Instinet Global Holdings, Inc., collectively, "Instinet").

                                    RECITALS

                  WHEREAS, Reuters is the common parent corporation of an
affiliated group of corporations within the meaning of Section 1504(a) of the
Code (as defined herein) and of consolidated, combined, unitary and other
similar groups as defined under similar laws of other jurisdictions;

                  WHEREAS, prior to the Restructuring (as defined herein),
certain Instinet Affiliates (as defined herein) were members of such affiliated,
consolidated, combined, unitary or other similar groups, and joined in filing
Reuters Consolidated Returns and Reuters Combined Returns (as defined herein);

                  WHEREAS, Reuters, Instinet Group LLC, a Delaware limited
liability company and their respective affiliates effected the Restructuring (as
defined herein) through a series of transactions;

                  WHEREAS, upon the conversion of Instinet Group LLC to a
corporation, Instinet Group Incorporated, Instinet Group Incorporated will
succeed to the rights and obligations of Instinet Group LLC with respect to this
Agreement;

                  WHEREAS, with respect to tax periods beginning on or after the
date of the Restructuring, Instinet and the Instinet Affiliates have not and
will not join in filing Reuters Consolidated Returns;

                  WHEREAS, with respect to tax periods beginning on or after the
date of the Restructuring, Instinet and the Instinet Affiliates have not and
will not join in filing Reuters Combined Returns in most jurisdictions, but may
continue to join in the filing of Reuters Combined Returns in some
jurisdictions;

                  WHEREAS, upon the conversion of Instinet Group LLC, Instinet
Group, Incorporated will become the new common parent of an affiliated group of
corporations within the meaning of Section 1504(a) of the Code consisting of
Instinet Group Incorporated and its includible affiliates;

                  WHEREAS, it is appropriate and desirable to set forth the
principles and responsibilities of the parties to this Agreement regarding the
allocation of Taxes (as
<PAGE>   5
defined herein) and other related liabilities and adjustments with respect to
Taxes, Audits (as defined herein) and other related Tax matters.

                  NOW THEREFORE, in consideration of the promises and the mutual
covenants contained herein and intending to be legally bound hereby, the parties
hereto hereby agree as follows:

SECTION 1. DEFINITIONS - Capitalized terms not otherwise defined herein shall
have the meanings ascribed to such terms in the Restructuring Agreement (as
defined herein). As used in this Agreement, capitalized terms shall have the
following meanings (such meanings to be equally applicable to both the singular
and plural forms of the terms defined).

                  "AUDIT" includes any audit, assessment of Taxes, other
examination by any Tax Authority, proceeding, or appeal of such a proceeding
relating to Taxes, whether administrative or judicial.

                  "CODE" means the Internal Revenue Code of 1986, as amended, or
any successor statute.

                  "COMBINED GROUP" means a group of corporations or other
entities that files (i) a Reuters Combined Return or (ii) an Instinet Combined
Return.

                  "CONSOLIDATED GROUP" means an affiliated group of corporations
within the meaning of Section 1504(a) of the Code.

                  "CONTROLLING PARTY" means with respect to a particular Tax
Return, the party entitled to control, contest, and represent the interests of
the parties in any Audit relating to a particular Tax Return under Section 7.1
of the Agreement.

                  "DECONSOLIDATION" means with respect to each Tax Return (i)
the event pursuant to which Instinet Global Holdings, Inc. and any Instinet
Affiliate ceased to be a subsidiary corporation includable in the Reuters
Consolidated Return, (ii) the event pursuant to which Instinet Global Holdings
Inc. and any Instinet Affiliate ceased to be included in a Reuters Combined
Return, (iii) the event pursuant to which Reuters and any Reuters Affiliate
ceased to be included in an Instinet Combined Return, (iv) any event (including
as a result of transactions contemplated by the Restructuring) pursuant to which
Tax Items relating to, or arising from, both the Transferred Business and the
Retained Business are no longer included on a Reuters Combined Return or an
Instinet Combined Return or (v) any event pursuant to which a Reuters Combined
Return or an Instinet Combined Return no longer includes Tax Items or Tax Assets
of both Reuters (or any Reuters Affiliate) and Instinet (or any Instinet
Affiliate).

                  "DECONSOLIDATION DATE" means with respect to each Tax Return
the day on which the Deconsolidation occurred.

                  "DECONSOLIDATION TAX" means any Tax, resulting from the
Deconsolidation, taken into account under Section 1.1502-13 or Section 1.1502-19
or any


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predecessor provision of the Treasury Regulations (or any similar provision
under Non-Federal Tax law).

                  "ESTIMATED TAX INSTALLMENT DATE" means the installments due
dates prescribed in Section 6655(c) of the Code (presently April 15, June 15,
September 15 and December 15).

                  "FEDERAL INCOME TAX" means any Tax imposed under Subtitle A of
the Code or any other provision of United States federal Income Tax law
(including the Taxes imposed by Sections 11, 55, 59A, and 1201(a) of the Code),
and any interest, additions to Tax or penalties applicable or related thereto.

                  "FEDERAL TAX" means any Tax imposed under the Code or
otherwise under United States federal Tax law.

                  "FINAL DETERMINATION" means the final resolution of any Tax
(or other matter) for a taxable period, including related interest or penalties,
that, under applicable law, is not subject to further appeal, review or
modification through proceedings or otherwise, including (1) by the expiration
of a statute of limitations or a period for the filing of claims for refunds,
amending Tax Returns, appealing from adverse determinations, or recovering any
refund (including by offset), (2) by a decision, judgment, decree, or other
order by a court of competent jurisdiction, which has become final and
unappealable, (3) by a closing agreement or an accepted offer in compromise
under Section 7121 or 7122 of the Code, or comparable agreements under laws of
other jurisdictions, (4) by execution of an Internal Revenue Service Form 870 or
870AD, or by a comparable form under the laws of other jurisdictions (excluding,
however, with respect to a particular Tax Item for a particular taxable period
any such form that reserves (whether by its terms or by operation of law) the
right of the taxpayer to file a claim for refund and/or the right of the Tax
Authority to assert a further deficiency with respect to such Tax Item for such
period), or (5) by any allowance of a refund or credit, but only after the
expiration of all periods during which such refund or credit may be recovered
(including by way of offset).

                  "INCOME TAX" means (a) any Tax based upon, measured by, or
calculated with respect to (1) net income or profits (including, without
limitation, any capital gains Tax, minimum Tax and any Tax on items of Tax
preference, but not including sales, use, real or personal property, gross or
net receipts, transfer or similar Taxes) or (2) multiple bases if one or more of
the bases upon which such Tax may be based, measured by, or calculated with
respect to, is described in clause (1) above, or (b) any United States state or
local franchise Tax.

                  "INDEMNIFIABLE LOSS DEDUCTION" has the meaning set forth in
Section 6.3(b) of this Agreement.

                  "INDEMNIFIED LOSS" has the meaning set forth in Section 6.3(b)
of this Agreement.



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                  "INDEMNITEE" has the meaning set forth in Section 6.3(b) of
this Agreement.


                  "INDEMNITOR" has the meaning set forth in Section 6.3(b) of
this Agreement.

                  "INDEPENDENT FIRM" has the meaning set forth in Section 4.4(b)
of this Agreement.

                  "INTEREST ACCRUAL PERIOD" has the meaning set forth in Section
6.4 of this Agreement.

                  "INSTINET AFFILIATE" means with respect to Instinet, any
corporation or other entity that directly, or indirectly through one or more
intermediaries, is controlled by, Instinet or any successor thereto. For
purposes of this definition, "control" means ownership, directly or indirectly,
of more than a fifty percent (50%) interest in such corporation or entity by
vote or value.

                  "INSTINET COMBINED RETURN" means any Tax Return with respect
to Non-Federal Taxes of Instinet (or any Instinet Affiliate) pursuant to which
Tax Items or Tax Assets of Reuters (or any Reuters Affiliate) or Tax Items
relating to or arising from both the Transferred Business and the Retained
Business, are included on a Tax Return of Instinet (or any Instinet Affiliate).

                  "INSTINET GROUP" means the affiliated group of corporations as
defined in Section 1504(a) of the Code, or similar group of entities as defined
under corresponding provisions of the laws of other jurisdictions following the
completion of the Restructuring, of which Instinet Global Holdings, Inc., or
upon conversion of Instinet Group LLC to a corporation, Instinet Group
Incorporated, is or was the common parent. Instinet Fixed Income, Inc. shall be
treated as if it were a member of the Instinet Group at all times prior to the
date of this agreement. Similarly, Reuters C Corp will be treated as if it were
a member of the Instinet Group for all periods ending on or prior to July 31,
2001.

                  "INSTINET GROUP COMBINED TAX LIABILITY" means, with respect to
any taxable period, the Instinet Group's liability for Non-Federal Combined
Taxes as determined under Section 4.3 of this Agreement.

                  "INSTINET GROUP FEDERAL INCOME TAX LIABILITY" means, with
respect to any taxable period, the Instinet Group's liability for Federal Income
Taxes as determined under Section 4.2 of this Agreement.

                  "INSTINET NON-FEDERAL COMBINED TAX" means any Non-Federal Tax
with respect to which an Instinet Combined Return is filed.

                  "INSTINET SEPARATE RETURN" means any Separate Return filed by
Instinet or any Instinet Affiliate.



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                  "NON-CONTROLLING PARTY" means with respect to a particular Tax
Return, the party not entitled to control, contest, and represent the interests
of the parties in any Audit relating to any Tax Return under Section 7.1 of the
Agreement.

                  "NON-FEDERAL COMBINED TAX" means any Non-Federal Tax with
respect to which a Reuters Combined Return or Instinet Combined Return is filed.

                  "NON-FEDERAL SEPARATE TAX" means any Non-Federal Tax other
than a Reuters Non-Federal Combined Tax or an Instinet Non-Federal Combined Tax.

                  "NON-FEDERAL TAX" means any Tax other than a Federal Tax.

                   "PAYMENT PERIOD" has the meaning set forth in Section 6.4 of
this Agreement.

                  "POST-DECONSOLIDATION PERIOD" means any taxable period with
respect to a Reuters Consolidated Return, Reuters Combined Return, or Instinet
Combined Return as the case may be, beginning after the applicable
Deconsolidation Date.

                  "PRE-DECONSOLIDATION PERIOD" means any taxable period with
respect to a Reuters Consolidated Return, Reuters Combined Return, or Instinet
Combined Return as the case may be, beginning on or before the close of business
on the applicable Deconsolidation Date.

                  "PRIVILEGE" means any privilege that may be asserted under
applicable law including, any privilege arising under or relating to the
attorney-client relationship (including the attorney-client and work product
privileges), the accountant-client privilege, and any privilege relating to
internal evaluation processes.

                  "PRO FORMA INSTINET GROUP COMBINED RETURN" means a pro forma
Non-Federal Combined Tax return or other schedule prepared pursuant to Section
4.3 of this Agreement.

                  "PRO FORMA INSTINET GROUP CONSOLIDATED RETURN" means a pro
forma consolidated Federal Income Tax return or other schedule prepared pursuant
to Section 4.2 of this Agreement.

                  "RESTATED TAX SAVING AMOUNT" has the meaning set forth in
Section 6.3(c) of this Agreement.

                  "RESTRUCTURING" means the series of transactions carried out
under (i) the Contribution Agreement between Reuters C Corp and Instinet Group
LLC, dated September 29, 2000, (ii) the Contribution Agreement between Reuters
Holdings Switzerland SA and Instinet Group LLC dated September 29, 2000, (iii)
the Asset Contribution Agreement between Instinet Corporation and Instinet Group
LLC dated July 31, 2000, and (iv) the Contribution Agreement between Instinet
Corporation and Instinet Group LLC dated July 25, 2000.



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                  "RESTRUCTURING TAX" means any Tax (net of any current benefit
arising from any Tax Asset) resulting from the Restructuring imposed upon
Reuters or any Reuters Affiliate or Instinet or any Instinet Affiliate; provided
that, such term shall not refer to the collateral Tax effects of the
Restructuring (including, without limitation, relating to the tax basis of
assets comprising the Transferred Business or the amount, if any, of Tax Assets
or earnings and profits of Instinet or any Instinet Affiliate following the
Restructuring).

                  "RETAINED BUSINESS" means all businesses retained by Reuters
or any Reuters Affiliate after the Restructuring.

                  "REUTERS AFFILIATE" means with respect to Reuters, any
corporation or other entity that directly, or indirectly through one or more
intermediaries, controls, is controlled by, or is under common control with
Reuters other than Instinet or any Instinet Affiliate. For purposes of this
definition, "control" means ownership, directly or indirectly, of more than a
fifty percent (50%) interest in such corporation or entity by vote or value.

                  "REUTERS COMBINED RETURN" means any Tax Return with respect to
Non-Federal Taxes (i) filed on a consolidated, combined (including nexus
combination, worldwide combination, domestic combination, line of business
combination or any other form of combination) or unitary basis wherein Instinet
or one or more Instinet Affiliates join in the filing of such Tax Return (for
any taxable period or portion thereof) with Reuters or one or more Reuters
Affiliates, or (ii) pursuant to which Tax Items or Tax Assets of Instinet (or
any Instinet Affiliate) or Tax Items relating to or arising from both the
Transferred Business and the Retained Business, are included on a Tax Return of
Reuters (or any Reuters Affiliate).

                  "REUTERS CONSOLIDATED GROUP" means an affiliated group of
corporations within the meaning of Section 1504(a) of the Code that files a
Reuters Consolidated Return.

                  "REUTERS CONSOLIDATED RETURN" means any Tax Return with
respect to Federal Income Taxes filed on a consolidated basis wherein Instinet
or one or more Instinet Affiliates join in the filing of such Tax Return (for
any taxable period or portion thereof) with Reuters or one or more Reuters
Affiliates.

                  "REUTERS GROUP" means the affiliated group of corporations as
defined in Section 1504(a) of the Code, or similar group of entities as defined
under corresponding provisions of the laws of other jurisdictions, of which
Reuters is the common parent, and any corporation or other entity which is a
member of such group for the relevant taxable period or portion thereof, but
excluding any member of the Instinet Group.

                  "REUTERS NON-FEDERAL COMBINED TAX" means any Non-Federal Tax
with respect to which a Reuters Combined Return is filed.



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                  "REUTERS SEPARATE RETURN" means any Separate Return filed by
Reuters or any Reuters Affiliate.

                  "SEPARATE RETURN" means any Tax Return with respect to
Non-Federal Separate Taxes filed by Reuters, Instinet, or any of their
respective Affiliates.

                  "SERVICE" means the Internal Revenue Service or any successor
agency or authority.

                  "STRADDLE PERIOD" means any taxable period with respect to a
Reuters Consolidated Return, Reuters Combined Return, or Instinet Combined
Return as the case may be, beginning on or before the applicable Deconsolidation
Date and ending after the applicable Deconsolidation Date.


                  "TAX" means any charges, fees, levies, imposts, duties, or
other assessments of a similar nature, including income, alternative or add-on
minimum, gross receipts, profits, lease, service, service use, wage, wage
withholding, employment, workers compensation, business occupation, occupation,
premiums, environmental, estimated, excise, employment, sales, use, transfer,
license, payroll, franchise, severance, stamp, windfall profits, withholding,
social security, unemployment, disability, ad valorem, highway use, commercial
rent, capital stock, paid up capital, recording, registration, property, real
property gains, value added, business license, custom duties, or other tax or
governmental fee of any kind whatsoever, imposed or required to be withheld by
any Tax Authority including any interest, additions to tax, or penalties
applicable or related thereto.


                  "TAX ASSET" means any Tax Item that could reduce a Tax,
including a net operating loss, net capital loss, investment tax credit, foreign
tax credit, charitable deduction or credit related to alternative minimum tax or
any other Tax credit.

                  "TAX AUTHORITY" means a governmental authority in the United
States or any subdivision, agency, commission or authority thereof or any
quasi-governmental or private body in the United States having jurisdiction over
the assessment, determination, collection or imposition of any Tax (including,
without limitation, the Service).

                  "TAX DETRIMENT" means an increase in the Tax liability of a
taxpayer (or of the affiliated group of which it is a member) for any taxable
period. Except as otherwise provided in this Agreement, a Tax Detriment shall be
deemed to have been realized or received from a Tax Item in a taxable period
only if and to the extent that the Tax liability of the taxpayer (or of the
affiliated group of which it is a member) for such period, after taking into
account the effect of the Tax Item on the Tax liability of such taxpayer in all
prior periods, is more than it would have been if such Tax liability were
determined without regard to such tax item.

                  "TAX ITEM" means any item of income, gain, loss, deduction or
credit, or other attribute that may have the effect of increasing or decreasing
any Tax.



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                  "TAX LAW" means any federal, state, local or foreign law with
respect to Taxes, including the Code and Treasury Regulations.

                  "TAX RETURN" means any return, report, certificate, form or
similar statement or document (including, any related or supporting information
or schedule attached thereto and any information return, amended tax return,
claim for refund or declaration of estimated tax) required to be supplied to, or
filed with, a Tax Authority in connection with the determination, assessment or
collection of any Tax or the administration of any laws, regulations or
administrative requirements relating to any Tax.

                  "TAX SAVING AMOUNT" has the meaning set forth in Section
6.3(b) of this Agreement.

                  "TRANSFERRED BUSINESS" means all assets, businesses, and
entities transferred under the control of the Instinet Group as a result of the
Restructuring.

                  "TRANSFER TAXES" means all Restructuring Taxes other than
Income Taxes that result from the transfer of any entities or assets under
Instinet or any Instinet Affiliate for purposes of effectuating the
Restructuring.

                  "TREASURY REGULATIONS" means the final, temporary and proposed
income tax regulations promulgated under the Code, as such regulations may be
amended from time to time (including corresponding provisions of succeeding
regulations).

SECTION 2. PREPARATION AND FILING OF TAX RETURNS.

         2.1 IN GENERAL. (a) Reuters shall have the sole and exclusive
responsibility for the preparation (except to the extent provided in Section 2.2
of this Agreement) and filing of: all Reuters Consolidated Returns, all Reuters
Combined Returns and all Reuters Separate Returns.

                  (b) Instinet shall, (subject to Section 2.2 of this Agreement)
be responsible for preparing and filing all Instinet Combined Returns and all
Instinet Separate Returns.

         2.2 MANNER OF PREPARING AND FILING TAX RETURNS. (a) All Tax Returns
filed after the date of this Agreement by Reuters, any Reuters Affiliate,
Instinet or any Instinet Affiliate shall be (1) prepared in a manner that is
consistent with Section 5 of this Agreement and the Code, and (2) filed on a
timely basis (taking into account applicable extensions) by the party
responsible for such filing under Section 2.1 of this Agreement.

                  (b) Reuters shall have the exclusive right, in its sole
discretion with respect to any Reuters Consolidated Return or Reuters Combined
Return to determine (1) the manner in which such Tax Return shall be prepared
and filed, including the elections, methods of accounting, positions,
conventions and principles of taxation to be used and the manner in which any
Tax Item shall be reported, (2) whether any extensions may be


                                       8
<PAGE>   12
requested, (3) the elections that will be made by Reuters, any Reuters
Affiliate, Instinet and any Instinet Affiliate on such Tax Return, (4) whether
any amended Tax Returns shall be filed, (5) whether any claims for refund shall
be made, (6) whether any refunds shall be paid by way of refund or credited
against any liability for the related Tax, and (7) whether to retain outside
firms to prepare or review such Tax Return. To the extent that any Tax Items of
Reuters are included on any Instinet Combined Return, Reuters shall also have
the right to determine the manner of reporting of such Tax Item.

                  (c) Instinet shall have the exclusive right with respect to
any Instinet Separate Returns or any Instinet Combined Return (subject to the
last sentence of Section 2.2(b) above) to determine (1) the manner in which such
Tax Return or Tax Items shall be prepared and filed, including the elections,
methods of accounting, positions, conventions and principles of taxation to be
used and the manner in which any Tax Item shall be reported, (2) whether any
extensions may be requested, (3) the elections that will be made by Instinet and
any Instinet Affiliate on such Tax Return or with respect to such Tax Items, (4)
whether any amended Tax Returns shall be filed, (5) whether any claims for
refund shall be made, (6) whether any refunds shall be paid by way of refund or
credited against any liability for the related Tax, and (7) whether to retain
outside firms to prepare or review such Tax Return or Tax Items; provided that,
if Reuters and any Reuters Affiliates together own directly or indirectly fifty
percent (50%) or more of the outstanding stock (by vote or value) of Instinet:
(i) Reuters shall, by the end of the relevant tax period, designate and notify
Instinet of the Instinet Separate Returns that it wishes to review and approve
and Instinet shall submit such Tax Returns to Reuters no later than fifteen (15)
business days prior to the due date for the filing of such Tax Returns (taking
into account applicable extensions) for Reuters review and approval, which
approval shall not be unreasonably withheld and (ii) Reuters shall have the
right to redetermine the manner of reporting of any Tax Item of Instinet
included in such Tax Returns including any of the matters listed in items 1
through 7 of this Section 2.2(c), if the proposed reporting of such Tax Item
would have a meaningful adverse effect with respect to the Taxes of Reuters or
any Reuters Affiliate, provided that the revised treatment of such Tax Item
could not result in the imposition of penalties on Instinet or any Instinet
Affiliate.

                  (d) In the event that a Tax Item on a Tax Return described in
Section 2.1(a) of this Agreement corresponds to a Tax Item on a Tax Return
described in Section 2.1(b) of this Agreement that is filed after the date of
this Agreement, Instinet or the Instinet Affiliate preparing, or causing the
preparation of, such Tax Return under Section 2.1(b) of this Agreement shall
conform the treatment of such Tax Item in such Tax Return described in Section
2.1(b) of this Agreement to the treatment of such Tax Item in the applicable Tax
Return described in Section 2.1(a) of this Agreement, provided that the revised
treatment of such Tax Item could not result in the imposition of penalties on
Instinet or any Instinet Affiliate and further provided that Reuters and any
Reuters Affiliate together own directly or indirectly fifty percent (50%) or
more of the outstanding stock (by vote or value) of Instinet.

                  (e) Instinet shall provide all reasonable and necessary
information to Reuters or its agents in order to facilitate the preparation of
the portions of the Reuters


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<PAGE>   13
Consolidated Returns and Reuters Combined Returns filed after the date of this
Agreement by Reuters (including making any related elections) that relate
exclusively to Instinet or any Instinet Affiliate or the Transferred Business.
Instinet shall submit this information to Reuters at least forty-five (45)
business days (or such shorter period as agreed to by Reuters) prior to the due
date for the filing of such Tax Returns (taking into account applicable
extensions). Instinet shall bear its pro rata share of the costs associated with
the preparation of such Tax Returns.

                  (f) Reuters shall provide all reasonable and necessary
information to Instinet or its agents in order to facilitate the preparation of
the portions of any Instinet Combined Returns (including making any related
elections) that relate exclusively to Reuters or any Reuters Affiliate. Reuters
shall submit this information to Instinet at least forty-five (45) business days
(or such shorter period as agreed to by Instinet) prior to the due date for the
filing of such Tax Returns (taking into account applicable extensions).

SECTION 3. PAYMENT OF TAXES TO TAX AUTHORITIES.

         3.1 FEDERAL INCOME TAXES. Reuters shall pay (or cause to be paid) to
the Service, all Federal Income Taxes with respect to any Reuters Consolidated
Return due and payable for all Pre-Deconsolidation Periods.

         3.2 NON-FEDERAL COMBINED TAXES. Reuters shall pay (or cause to be paid)
to the appropriate Tax Authorities all Reuters Non-Federal Combined Taxes due
and payable for all Pre-Deconsolidation Periods. Instinet shall pay (or cause to
be paid) to the appropriate Tax Authorities all Instinet Non-Federal Combined
Taxes due and payable for all Pre-Deconsolidation Periods.

         3.3 NON-FEDERAL SEPARATE TAXES. The parties shall each pay (or cause to
be paid) to the appropriate Tax Authorities all of their respective Non-Federal
Separate Taxes.

         3.4 OTHER FEDERAL TAXES. The parties shall each pay (or cause to be
paid) to the appropriate Tax Authorities all of their respective Federal Taxes
(excluding Federal Income Taxes for Pre-Deconsolidation Periods which are
governed by Section 3.1 of this Agreement).

SECTION 4. ALLOCATION OF TAXES.

         4.1 INSTINET LIABILITY FOR FEDERAL INCOME TAXES AND NON-FEDERAL
COMBINED TAXES. For each Pre-Deconsolidation Period, Instinet shall be liable
for and shall pay to Reuters an amount equal to the sum of the Instinet Group
Federal Income Tax Liability and the Instinet Group Combined Tax Liability for
such taxable period.

         4.2 INSTINET GROUP FEDERAL INCOME TAX LIABILITY. With respect to each
Pre-Deconsolidation Period, the Instinet Group Federal Income Tax Liability for
such taxable period shall be the Instinet Group's liability for Federal Income


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Taxes and any interest, penalties and other additions to such taxes, for such
taxable period, as determined on a Pro Forma Instinet Group Consolidated Return
prepared:

                  (a) on a basis consistent with the preparation of the Reuters
Consolidated Return for such period (including whether regular Tax or federal
alternative minimum Tax applies with respect to the Reuters Consolidated
Return), determined by including only Tax Items of members of the Instinet Group
which are included in the Reuters Consolidated Return and by allocating Tax
Assets to the Instinet Group to the extent that the Tax Asset was created by a
member of the Instinet Group and such Tax Asset was actually utilized on the
relevant Reuters Consolidated Return; and

                  (b) applying the highest statutory marginal corporate income
Tax rate in effect for such taxable period (or portion thereof); provided that,
in the event that the federal alternative minimum Tax applies to the Reuters
Consolidated Return, the Instinet Group Federal Income Tax Liability shall equal
the lesser of (i) the alternative minimum Tax liability with respect to the
Reuters Consolidated Return that would result by including only Tax Items and
Tax Assets of members of the Instinet Group included in the Reuters Consolidated
Return or (ii) the aggregate Tax liability payable with respect to such Reuters
Consolidated Return.

                  (c) The Instinet Group Federal Income Tax Liability for a
Straddle Period shall be calculated based solely on the portion of such Straddle
Period during which Instinet was included in the Reuters Consolidated Group.

         4.3 INSTINET GROUP COMBINED TAX LIABILITY. With respect to any
Pre-Deconsolidation Period, the Instinet Group Combined Tax Liability shall be
the sum for such taxable period of the Instinet Group's liability for each
Non-Federal Combined Tax, as determined on Pro Forma Instinet Group Combined
Returns prepared in a manner consistent with the principles and procedures set
forth in Section 4.2 hereof.

         4.4 COOPERATION.

                  (a) Reuters and Instinet shall prepare jointly any Pro Forma
Instinet Group Consolidated Returns and Pro Forma Instinet Group Combined
Returns. Reuters and Instinet agree to cooperate in good faith in connection
with the preparation of such pro forma tax returns and agree to make reasonably
available any documents, information or employees in connection therewith.

                  (b) The Pro Forma Instinet Group Consolidated Returns and Pro
Forma Instinet Group Combined Returns shall be completed no later than sixty
(60) business days following the date on which the related Reuters Consolidated
Return, Reuters Combined Return or Instinet Combined Return, as the case may be,
is filed with the appropriate Tax Authority. In the event there are any disputes
relating to the reporting of any Tax Item on the pro forma tax returns, Reuters
and Instinet shall in good faith attempt to resolve their disagreement. If such
dispute is not resolved within sixty (60) business days following the
commencement of the dispute, Reuters and Instinet shall jointly retain a tax
attorney that is a member of a nationally recognized law firm or "big


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<PAGE>   15
five" accounting firm, which firm is independent of both parties (the
"Independent Firm"), to resolve the dispute. The Independent Firm shall act as
an arbitrator to resolve all points of disagreement and its decision shall be
final and binding upon all parties involved. Following the decision of the
Independent Firm, Reuters and Instinet shall each take or cause to be taken any
action necessary to implement the decision of the Independent Firm. The fees and
expenses relating to the Independent Firm shall be borne equally by Reuters and
Instinet.

         4.5 TAX SHARING INSTALLMENT PAYMENTS. (a) FEDERAL INCOME TAXES. Not
later than 2 business days prior to each Estimated Tax Installment Date with
respect to any Pre-Deconsolidation Period, the parties shall, consistent with
past practice, determine under the principles of Section 6655 of the Code the
estimated amount of the related installment of the Instinet Group Federal Income
Tax Liability. Instinet shall pay to Reuters no later than five (5) business
days after such Estimated Tax Installment Date the amount thus determined.

                  (b) NON-FEDERAL COMBINED TAXES. (1) REUTERS TAX RETURNS.
Reuters shall, in connection with any installment payment (payable with respect
to any Reuters Combined Return) with respect to Non-Federal Combined Taxes for
any Pre-Deconsolidation Period, consistent with past practice, determine the
estimated amount of the related installment of the Instinet Group Combined Tax
Liability. Within the first ten (10) business days of any month, Reuters may
provide Instinet with a written statement setting forth amounts owed by Instinet
in connection with any installment payments with respect to Non-Federal Combined
Taxes made by Reuters for the immediately preceding month and any other month
for which a statement has not previously been provided by Reuters. Instinet
shall pay the amounts set forth on any statement within seven (7) business days
following the receipt of such statement.

                  (2) INSTINET TAX RETURNS. Instinet shall, in connection with
any installment payment (payable with respect to any Instinet Combined Return)
with respect to Non-Federal Combined Taxes for any Pre-Deconsolidation Period,
consistent with past practice, determine the estimated amount of the related
installment of the Instinet Group Combined Tax Liability. Within the first ten
(10) business days of any month, Instinet may provide Reuters with a written
statement setting forth amounts owed by Reuters in connection with any
installment payments with respect to Non-Federal Combined Taxes made by Instinet
for the immediately preceding month and any other month for which a statement
has not previously been provided by Instinet. The amount payable by Reuters
pursuant to the immediately preceding sentence shall equal the aggregate amount
of the installment payment made by Instinet less the estimated amount of the
Instinet Group Combined Tax Liability related to such installment as determined
in the first sentence of this Section 4.5(b). Reuters shall pay the amounts set
forth on any statement within seven (7) business days following the receipt of
such statement.

         4.6 TAX SHARING TRUE-UP PAYMENTS. (a) FEDERAL INCOME TAXES. Not later
than fifteen (15) business days following the completion of any Pro Forma
Instinet Group Consolidated Return, Instinet shall pay to Reuters, or Reuters
shall pay to Instinet, as appropriate, an amount equal to the difference, if
any, between the


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<PAGE>   16
Instinet Group Federal Income Tax Liability for the Pre-Deconsolidation Period
and the aggregate amount paid by Instinet with respect to such period under
Section 4.5(a) of this Agreement.

                  (b) NON-FEDERAL COMBINED TAXES. Not later than fifteen (15)
business days following the completion of any Pro Forma Instinet Group Combined
Return, Instinet shall pay to Reuters, or Reuters shall pay to Instinet, as
appropriate, an amount equal to the difference, if any, between the Instinet
Group Combined Tax Liability for the Pre-Deconsolidation Period and the amounts
paid by Instinet with respect to such period under Sections 4.5(b)(1) and (b)(2)
of this Agreement. For purposes of this Section 4.6(b), the amounts paid by
Instinet under (i) Section 4.5(b)(1) shall be the amounts paid to Reuters and
(ii) Section 4.5(b)(2) shall be the amounts paid to the relevant Tax Authority
less any amounts received from Reuters.

         4.7 REDETERMINATION AMOUNTS. For any Pre-Deconsolidation Period, in the
event of (i) a redetermination of any Tax Item as a result of a Final
Determination, (ii) the filing of a Tax refund claim, or (iii) the filing of an
amended Tax Return pursuant to which Taxes are paid to a Tax Authority or a
refund of Taxes is received from a Tax Authority, Reuters and Instinet shall
prepare jointly, in accordance with the principles and procedures set forth in
this Section 4, Pro Forma Instinet Group Consolidated Returns and Pro Forma
Instinet Group Combined Returns, as appropriate, both without regard to the
redetermined Tax Item and with regard to the redetermined Tax Item. Instinet
shall pay to Reuters the amount by which the Tax liability reflected on the pro
forma tax return with regard to the redetermined Tax Item exceeds the Tax
liability reflected on the pro forma tax return without regard to the
redetermined Tax Item, and Reuters shall pay to Instinet the amount by which the
Tax liability reflected on the pro forma tax return without regard to the
redetermined Tax Item exceeds the Tax liability reflected on the pro forma tax
return with regard to the redetermined Tax Item.

         4.8 PAYMENT OF TAXES FOR POST-DECONSOLIDATION PERIODS. Except as
otherwise provided in this Agreement, Reuters shall pay or cause to be paid all
Taxes and shall be entitled to receive and retain all refunds of Taxes with
respect to Tax Returns relating to Post-Deconsolidation Periods for which
Reuters has filing responsibility, including under this Agreement. Except as
otherwise provided in this Agreement, Instinet shall pay or cause to be paid all
Taxes and shall be entitled to receive and retain all refunds of Taxes with
respect to Tax Returns relating to Post- Deconsolidation Periods for which
Instinet has filing responsibility, including under this Agreement. All refunds
of Taxes with respect to any Straddle Period shall be allocated to the party
generating such refund in accordance with the principles upon which the pro
forma amounts of Taxes are allocated to the parties under this Section 4.

SECTION 5. TAX ATTRIBUTES.

         5.1 ALLOCATION OF TAX ITEMS. All Tax computations for (i) any
Pre-Deconsolidation Period ending on the Deconsolidation Date, (ii) the
immediately following taxable period of Instinet or any Instinet Affiliate and
(iii) any Straddle Period, shall be made pursuant to the principles of Section
1.1502-76(b) of the Treasury


                                       13
<PAGE>   17
Regulations or of a corresponding provision under the laws of other
jurisdictions and, to the extent possible, in a manner consistent with the
principles set forth in Section 4.2(a) of this Agreement.

         5.2 POST DECONSOLIDATION. To the extent permitted by applicable law,
following the Deconsolidation, the relevant Tax Assets with respect to the
Reuters Consolidated Group or Reuters Combined Group, as the case may be, shall
be allocated to the corporation or entity that created or generated the Tax
Asset.

SECTION 6. ADDITIONAL OBLIGATIONS.

         6.1 PROVISION OF INFORMATION AND MUTUAL COOPERATION. (a) Reuters and
Instinet shall, and shall cause their respective affiliates to, (1) furnish to
the other in a timely manner such information, documents and other materials as
the other may reasonably request for purposes of (i) preparing any Tax Return
(or pro forma tax return prepared in accordance with Section 4 hereof) or
portion thereof for which the other has responsibility for preparing under this
Agreement, (ii) contesting or defending any Audit, and (iii) making any
determination or computation necessary or appropriate under this Agreement, (2)
make its employees reasonably available to the other to provide explanations of
documents and materials and such other information as the other may reasonably
request in connection with any of the matters described in subclauses (i), (ii)
and (iii) of clause (1) above, (3) reasonably cooperate in connection with any
Audit. With respect to any taxable period in which Reuters and any Reuters
Affiliates together own directly or indirectly, 50% or more of the outstanding
stock (by vote or value) of Instinet, Instinet shall, at Reuters request,
provide Reuters with copies of any Instinet Separate Returns and Instinet
Combined Returns.

                  (b) Reuters and Instinet shall, and shall cause their
respective affiliates to, retain books, records, documentation or other
information relating to any Tax Return or Audit, with respect to any taxable
period in which Reuters and any Reuters Affiliates together own, directly or
indirectly, 50% or more of the outstanding stock (by vote or value) of Instinet,
until the later of (i) the expiration of the applicable statute of limitations
(after giving effect to any extension, waiver, or mitigation thereof) and (ii)
in the event any claim is made under this Agreement or by any Tax Authority for
which such information is relevant, until a Final Determination is reached with
respect to such claim. Notwithstanding anything to the contrary included in this
Agreement, the parties will comply in all respects with the requirements of any
applicable record retention agreement with the Service or other Tax Authority.

                  (c) Notwithstanding any other provision of this Agreement, no
member of the Reuters Group shall be required to provide Instinet or any
Instinet Affiliate access to or copies of (1) any Tax information that relates
exclusively to any member of the Reuters Group, (2) any Tax information as to
which any member of the Reuters Group is entitled to assert the protection of
any Privilege, or (3) any Tax information as to which any member of the Reuters
Group is subject to an obligation to maintain the confidentiality of such
information. Reuters shall use reasonable efforts to separate any such
information from any other information to which Instinet is entitled to


                                       14
<PAGE>   18
access or to which Instinet is entitled to copy under this Agreement, to the
extent consistent with preserving its rights under this Section 6.1(c).

                  (d) Notwithstanding any other provision of this Agreement,
with respect to Tax information that relates to any taxable period in which
Instinet is no longer included in the Reuters Consolidated Group and no Reuters
Combined Return or Instinet Combined Return is filed, and during which period
Reuters and any Reuters Affiliate together do not own directly or indirectly,
50% or more of the outstanding stock (by vote or value) of Instinet, no member
of the Instinet Group shall be required to provide Reuters or any Reuters
Affiliate access to or copies of (1) any Tax information that relates
exclusively to any member of the Instinet Group (2) any Tax information as to
which any member of the Instinet Group is entitled to assert the protection of
any Privilege or (3) any Tax information as to which any member of the Instinet
Group is subject to an obligation to maintain the confidentiality of such
information. Instinet shall use reasonable efforts to separate any such
information from any other information to which Reuters is entitled to access or
to which Reuters is entitled to copy under this Agreement, to the extent
consistent with preserving its rights under this Section 6.1(d).

         6.2 INDEMNIFICATION. FAILURE TO PAY. Reuters and each Reuters Affiliate
shall jointly and severally indemnify Instinet, each Instinet Affiliate and
their respective directors, officers and employees, and hold them harmless from
and against any Tax or any loss, liability, claim, damage or expense
(collectively, a "Loss") that is attributable to, or results from the failure of
Reuters or any Reuters Affiliate to make any payment required to be made under
this Agreement. Instinet and each Instinet Affiliate shall jointly and severally
indemnify Reuters, each Reuters Affiliate and their respective directors,
officers and employees, and hold them harmless from and against any Tax or Loss
that is attributable to, or results from, the failure of Instinet or any
Instinet Affiliate to make any payment required to be made under this Agreement.

                  (a) INACCURATE OR INCOMPLETE INFORMATION. Reuters and each
Reuters Affiliate shall jointly and severally indemnify Instinet, each Instinet
Affiliate and their respective directors, officers and employees, and hold them
harmless from and against any Tax or Loss attributable to the negligence of
Reuters or any Reuters Affiliate in supplying Instinet or any Instinet Affiliate
with inaccurate or incomplete information, in connection with the preparation of
any Tax Return or any Audit. Instinet and each Instinet Affiliate shall jointly
and severally indemnify Reuters, each Reuters Affiliate and their respective
directors, officers and employees, and hold them harmless from and against any
Tax or Loss attributable to the negligence of Instinet or any Instinet Affiliate
in supplying Reuters or any Reuters Affiliate with inaccurate or incomplete
information, in connection with the preparation of any Tax Return or any Audit.

         6.3 TAX CONSEQUENCES OF PAYMENTS. TAX CHARACTERIZATION OF PAYMENTS. For
all Tax purposes and notwithstanding any other provision of this Agreement, to
the extent permitted by applicable law, the parties hereto shall treat any
payment made pursuant to this Agreement (other than any payment made in
satisfaction of an intercompany obligation) as a capital contribution or
dividend distribution, as the case may be, immediately prior to the applicable


                                       15
<PAGE>   19
Deconsolidation Date and, accordingly, as not includible in the taxable income
of the recipient. If, as a result of a Final Determination, it is determined
that the receipt or accrual of any payment made under this Agreement is taxable
to the Indemnitee (as defined in Section 6.3(b) of this Agreement), the
Indemnitor (as defined in Section 6.3(b) of this Agreement) shall pay to the
Indemnitee an amount equal to any increase in the Income Taxes of the Indemnitee
as a result of receiving the payment from the Indemnitor (grossed up to take
into account such payment, if applicable).

                  (a) ADJUSTMENTS TO PAYMENTS. Any party that has received a
payment ("Indemnitee") under this Agreement from another party ("Indemnitor")
with respect to any Losses or Taxes suffered or incurred by the Indemnitee
("Indemnified Loss") shall pay to such Indemnitor an amount equal to any "Tax
Saving Amount" realized by the Indemnitee promptly upon its receipt. For
purposes of this Section 6.3(b), the Tax Saving Amount shall equal the amount by
which the Income Taxes of the Indemnitee or any of its affiliates are reduced
(including, without limitation, through the receipt of a refund, credit or
otherwise), plus any related interest received from a Tax Authority, as a result
of claiming as a deduction or offset on any relevant Tax Return amounts
attributable to an Indemnified Loss (the "Indemnifiable Loss Deduction").

                  (b) REPORTING OF INDEMNIFIABLE LOSS. In the event that an
Indemnitee incurs an Indemnified Loss, such Indemnitee shall claim as a
deduction or offset on any relevant Tax Return (including, without limitation,
any claim for refund) such Indemnified Loss to the extent such position is
supported by "substantial authority" (within the meaning of Section 1.6662-4(d)
of the Treasury Regulations) with respect to United States federal, state and
local Tax Returns or has similar appropriate authoritative support with respect
to any Tax Return other than United States federal, state and local Tax Returns.
The Indemnitee shall have primary responsibility for the preparation of its Tax
Returns and reporting thereon such Indemnifiable Loss Deduction; provided, that
the Indemnitee shall consult with, and provide the Indemnitor with a reasonable
opportunity to review and comment on the portion of the Indemnitee's Tax Return
relating to the Indemnified Loss. If a dispute arises between the Indemnitee and
the Indemnitor as to whether there is "substantial authority" (with respect to
United States federal, state and local Tax Returns) or similar appropriate
authoritative support (with respect to any Tax Return other than United States
federal, state and local Tax Returns) for the claiming of an Indemnifiable Loss
Deduction, such dispute shall be resolved in accordance with the principles and
procedures set forth in Section 4.4(b) of this Agreement. Both Reuters and
Instinet shall act in good faith to coordinate their Tax Return filing positions
with respect to the taxable periods that include an Indemnifiable Loss
Deduction. There shall be an adjustment to any Tax Saving Amount calculated
under Section 6.3(b) hereof in the event of an Audit which results in a Final
Determination that increases or decreases the amount of the Indemnifiable Loss
Deduction reported on any relevant Tax Return of the Indemnitee. The Indemnitee
shall promptly inform the Indemnifying Party of any such Audit and shall attempt
in good faith to sustain the Indemnifiable Loss Deduction at issue in the Audit.
Upon receiving a written notice of a Final Determination in respect of an
Indemnifiable Loss Deduction, the Indemnitee shall redetermine the Tax Saving
Amount attributable to the Indemnifiable Loss Deduction under Section 6.3(b)
hereof, taking into account the Final Determination (the "Restated Tax Saving
Amount"). If the Restated


                                       16
<PAGE>   20
Tax Saving Amount is greater than the Tax Saving Amount, the Indemnitee shall
promptly pay the Indemnitor an amount equal to the difference between such
amounts. If the Restated Tax Saving Amount is less than the Tax Saving Amount,
then the Indemnitor shall promptly pay the Indemnitee an amount equal to the
difference between such amounts.

         6.4 INTEREST. Payments pursuant to this Agreement that are not made
within the period prescribed in this Agreement or, if no period is prescribed,
within fifteen (15) business days after demand for payment is made (the "Payment
Period") shall bear interest for the period from and including the date
immediately following the last date of the Payment Period through and including
the date of payment (the "Interest Accrual Period") at a per annum rate equal to
the long-term applicable federal rate ("AFR") in effect on the last day of such
Payment Period, plus 200 basis points. Such interest will be payable at the same
time as the payment to which it relates and shall be calculated on the basis of
a year of 365 days and the actual number of days for which due.

SECTION 7. AUDITS.

         7.1 IN GENERAL. (a) Reuters shall have the exclusive right, in its sole
discretion, to control, contest, and represent the interests of Reuters, any
Reuters Affiliate, Instinet or any Instinet Affiliate in any Audit relating to
any Reuters Consolidated Return, any Reuters Combined Return, or any Reuters
Separate Return and to resolve, settle or agree to any deficiency, claim or
adjustment proposed, asserted or assessed in connection with or as a result of
any such Audit.

                  (b) Instinet shall have the exclusive right, in its sole
discretion, to control, contest, and represent the interests of Instinet or any
Instinet Affiliate in any Audit relating to any Instinet Separate Return or any
Instinet Combined Return and to resolve, settle, or agree to any deficiency,
claim or adjustment proposed, asserted or assessed in connection with or as a
result of any such Audit; provided that, so long as Reuters and any Reuters
Affiliates together own fifty percent (50%) or more of the outstanding stock (by
vote or value) of Instinet, Instinet or the relevant Instinet Affiliate shall
keep Reuters apprised of any significant contact with the relevant Tax Authority
and, at the request of Reuters, provide copies of any notices, correspondence or
documents provided to or received from the relevant Tax Authority. All positions
taken by Instinet in such Audit shall be consistent with the position reported
on the relevant Instinet Tax Return; provided that, if Instinet wishes to take
any position contrary to the position previously taken on such Tax Return,
Instinet shall immediately notify Reuters of such change in position and if such
position would have a meaningful adverse effect on Reuters, then Reuters shall
have the right to require Instinet to follow its prior reporting position or any
other position in connection with such Audit.

                  (c) Reuters' and Instinet's rights shall extend to any matter
pertaining to the management and control of an Audit, including, without
limitation, execution of waivers, choice of forum, scheduling of conferences and
the resolution of any Tax Item.



                                       17
<PAGE>   21
         7.2 NOTICE. If after the date of this Agreement, Reuters (or any
Reuters Affiliate) or Instinet (or any Instinet Affiliate) receives written
notice of, or relating to, an Audit from a Tax Authority that asserts, proposes
or recommends a deficiency, claim or adjustment that, if sustained, could result
in Taxes for which the other party is responsible under this Agreement, then the
party receiving such notice shall provide a copy of such notice to such other
party within ten (10) days of receipt thereof.

         7.3 PARTICIPATION RIGHTS. (a) If a Tax Authority asserts, proposes or
recommends a deficiency, claim or adjustment that, if sustained, would result in
Taxes for which the Non-Controlling Party is responsible under this Agreement,
then the Controlling Party shall keep the Non-Controlling Party informed in a
timely manner of all material actions taken or proposed to be taken by the
Controlling Party in connection with such deficiency, claim or adjustment.

                  (b) in the case of an Audit with respect to a Tax Item for
which the Non-Controlling Party would be primarily responsible under this
Agreement, the Controlling Party shall, if it is reasonably satisfied that it
will not adversely affect the Controlling Party:

                           (i) in the case of any material correspondence or
filing submitted to the Tax Authority or any judicial authority that relates to
the merits of such deficiency, claim or adjustment (1) reasonably in advance of
such submission, but subject to applicable time constraints imposed by such Tax
Authority or judicial authority, provide the Non-Controlling Party with a draft
copy of the portion of such correspondence or filing that relates to such
deficiency, claim or adjustment, (2) incorporate, subject to applicable time
constraints imposed by such Tax Authority or judicial authority, the
Non-Controlling Party's acceptable comments and changes on such draft copy of
such correspondence or filing, and (3) provide the Non-Controlling Party with a
final copy of the portion of such correspondence or filing that relates to such
deficiency, claim or adjustment; and

                           (ii) provide the Non-Controlling Party with notice
reasonably in advance of, and the Non-Controlling Party shall have the right to
attend, any meetings with the Tax Authority (including meetings with examiners)
or hearings or proceedings before any judicial authority to the extent they
relate to such deficiency, claim or adjustment.

                  (c) If the Controlling Party is reasonably satisfied that it
will not adversely affect the Controlling Party:

                           (i) the Controlling Party shall accept any reasonable
suggestions made by the Non-Controlling Party with respect to the resolution or
settlement of, or agreement to, any deficiency, claim or adjustment proposed,
asserted or assessed in connection with or as a result of any Audit with respect
to a Tax Item for which the Non-Controlling Party would be primarily responsible
under this Agreement; and



                                       18
<PAGE>   22
                           (ii) the Controlling Party shall accept any
reasonable request of the Non-Controlling Party to contest or continue to
contest any deficiency, claim or adjustment proposed, asserted or assessed in
connection with or as a result of any Audit with respect to any Tax Item for
which the Non-Controlling Party would be primarily responsible under this
Agreement provided that (A) the Non-Controlling Party shall have agreed to pay,
and shall be currently paying, all reasonable out of pockets costs and expenses
incurred by the Controlling Party to contest such deficiency, claim or
assessment including reasonable outside attorney's, accountant's and
investigatory fees and disbursements, (B) the Non-Controlling Party agrees to
make provision satisfactory to the Controlling Party for the proposed
deficiency, and (C) the Non-Controlling Party agrees to indemnify the
Controlling Party for any increased Tax liability that may result from the
continued contest of such Tax Item.

                  (d) At the Controlling Party's reasonable request (or upon the
Controlling Party's consent to a request by the Non-Controlling Party, which
consent shall not be unreasonably withheld), the Non-Controlling Party shall
assume responsibility for (1) presenting the merits with respect to (A) any
deficiency, claim or adjustment that, if sustained, would result in Taxes for
which the Non-Controlling Party is responsible under this Agreement, or (B)
subject to Section 7.5 of this Agreement, any affirmative claim relating to a
Tax Item of the Non-Controlling Party, or (2) resolving, settling or agreeing to
any such deficiency, claim or adjustment with the express consent of the
Controlling Party. Any such request (or consent) by the Controlling Party shall
be subject to the Non-Controlling Party's continued compliance with the
conditions of Section 7.4 of this Agreement and to such other conditions as the
Controlling Party reasonably determines to be appropriate to preserve the
Controlling Party's rights described in Section 7.1(a) or (b) of this Agreement.

         7.4 SETTLEMENT. The Controlling Party may resolve, settle or agree to
any deficiency, claim or adjustment proposed, asserted or assessed in connection
with any Audit of any Tax Return that it controls under Section 7.1 of this
Agreement without the Non-Controlling Party's consent unless:

                           (i) such resolution, settlement or agreement relates
to (A) Tax Items that in the aggregate exceed two hundred and fifty thousand
dollars ($250,000) for which the Non-Controlling Party could be liable, and,

                           (iii) the Non-Controlling Party delivers to the
Controlling Party, within thirty (30) days of a reasonable request by the
Controlling Party, a written opinion of nationally recognized tax counsel, to
the effect that the Non-Controlling Party's position with respect to such
deficiency, claim or adjustment would more likely than not prevail upon appeal
in a manner favorable to the Non-Controlling Party.

         7.5 AFFIRMATIVE CLAIMS. (a) IN GENERAL. Subject to the principles of
Sections 7.3 and 7.4 of this Agreement, Reuters shall assert any affirmative
claim (including, without limitation, by filing an amended return or claim for
refund) relating to a Tax Item of a member of the Instinet Group to the relevant
Tax Authority


                                       19
<PAGE>   23
provided that (1) Instinet agrees in advance to provide full compensation to
Reuters for any cost or detriment, including any additional Tax liability
resulting from the filing of such amended return or claim for refund, to Reuters
or a Reuters Affiliate that would result from successfully asserting such claim,
and (2) Instinet reasonably requests that such claim be asserted within the
applicable time period set forth in Section 7.5(b) or 7.5(c) of this Agreement.
Reuters may, in its sole discretion, assert any affirmative claim that does not
satisfy the foregoing conditions or that it is not described in Section 7.5(b)
or 7.5(c) of this Agreement. Subject to the principles of Sections 7.3 and 7.4
of this Agreement, Instinet shall assert any affirmative claim (including,
without limitation, by filing an amended return or claim for refund) relating to
a Tax Item of a member of the Reuters Group to the relevant Tax Authority
provided that (1) Reuters agrees in advance to provide full compensation to
Instinet for any cost or detriment, including any additional Tax liability
resulting from the filing of such amended return or claim for refund, to
Instinet or an Instinet Affiliate that would result from successfully asserting
such claim, and (2) Reuters reasonably requests that such claim be asserted
within the applicable time period set forth in Section 7.5(d) of this Agreement.
Instinet may, in its sole discretion, assert any affirmative claim that does not
satisfy the foregoing conditions or that it is not described in Section 7.5(d)
of this Agreement.

                  (b) REUTERS CONSOLIDATED RETURNS. Instinet shall request that
Reuters assert any affirmative claims relating to a Tax Item of a member of the
Instinet Group for a Reuters Consolidated Return no later than the date that is
one hundred eighty (180) days after the date on which Reuters delivers written
notice to Instinet that an examination of the Reuters Consolidated Return for
the applicable year is to begin.

                  (c) REUTERS COMBINED RETURNS. Instinet shall request that
Reuters assert any affirmative claims relating to a Tax Item of a member of the
Instinet Group for a Pre-Deconsolidation Period for which a Reuters Combined
Return has been filed no later than the date that is one hundred eighty (180)
days (but subject to applicable time constraints imposed by the Tax Authority)
after the date on which Reuters delivers written notice to Instinet that an
examination of the Reuters Combined Return for the applicable
Pre-Deconsolidation Period has begun or is to begin.

                  (d) INSTINET COMBINED RETURNS. Reuters shall request that
Instinet assert any affirmative claims relating to a Tax Item of a member of the
Reuters Group for a Pre-Deconsolidation Period for which an Instinet Combined
Return has been filed no later than the date that is one hundred eighty (180)
days (but subject to applicable time constraints imposed by the Tax Authority)
after the date on which Instinet delivers written notice to Reuters that an
examination of the Instinet Combined Return for the applicable
Pre-Deconsolidation Period has begun or is to begin.

SECTION 8. LIABILITY FOR RESTRUCTURING TAXES AND DECONSOLIDATION TAXES.
Notwithstanding any other provision of this Agreement Instinet shall be
responsible for the payment of and shall indemnify and hold Reuters harmless
from and against any Restructuring Taxes or Deconsolidation Taxes in the nature
of Transfer Taxes, and Reuters shall be responsible for the payment of, and
shall


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<PAGE>   24
indemnify and hold Instinet harmless from and against, any Restructuring Taxes
or Deconsolidation Taxes in the nature of Income Taxes imposed upon Reuters.

SECTION 9. MISCELLANEOUS.

         9.1 EFFECTIVENESS. This Agreement shall become effective upon execution
by both parties hereto.

         9.2 NOTICES. All notices, requests, demands and other communications
under this Agreement shall be in writing and, unless otherwise provided herein,
shall be deemed to have been duly given (i) on the date of service if served
personally on the party to whom notice is given, (ii) on the day of transmission
if sent via facsimile transmission to the facsimile number given below;
provided, telephonic confirmation of receipt is obtained promptly after
completion of transmission, (iii) on the business day after delivery to an
overnight courier service or the Express mail service maintained by the United
States Postal Service; provided, receipt of delivery has been confirmed, or (iv)
on the fifth day after mailing; provided, receipt of delivery is confirmed, if
mailed to the party to whom notice is to be given, by first class mail,
registered or certified, postage prepaid, properly addressed and return-receipt
requested, to the party as follows:

                  If to Reuters or any Reuters Affiliate, to:

                  Vice President, Tax
                  Reuters America Holdings LLC
                  3 Times Square
                  New York, NY 10036

                  If to Instinet or any Instinet Affiliate to:

                  Vice President, Taxes
                  Instinet Group, LLC
                  850 Third Avenue
                  New York, New York 10022

                  Any party may change its address or fax number by giving the
other party written notice of its new address or fax number in the manner set
forth above.

         9.3 CHANGES IN LAW. Any reference to a provision of the Code or a law
of another jurisdiction shall include a reference to any applicable successor
provision or law.

         9.4 SUCCESSORS AND ASSIGNS. This Agreement and all of the provisions
hereof shall be binding upon and inure to the benefit of the parties and their
respective successors and permitted assigns, but neither this Agreement nor any
of the rights, interests or obligations hereunder shall be assigned by either
party without the prior written consent of the other party.



                                       21
<PAGE>   25
         9.5 AUTHORIZATION, ETC. Each of the parties hereto hereby represents
and warrants that it has the power and authority to execute, deliver and perform
this Agreement, that this Agreement has been duly authorized by all necessary
corporate action on the part of such party, that this Agreement constitutes a
legal, valid and binding obligation of each such party and that the execution,
delivery and performance of this Agreement by such party does not contravene or
conflict with any provision of law or of its charter or bylaws or any agreement,
instrument or order binding on such party.

         9.6 COMPLETE AGREEMENT. This Agreement shall constitute the entire
agreement between Reuters or any Reuters Affiliate and Instinet or any Instinet
Affiliate with respect to the subject matter hereof and shall supersede all
previous negotiations, commitments and writings with respect to such subject
matter. Unless the context indicates otherwise, any reference to Instinet in
this Agreement shall refer to Instinet and the Instinet Affiliates and any
reference to Reuters in this Agreement shall refer to Reuters and the Reuters
Affiliates.

         9.7 INTERPRETATION. The Section headings contained in this Agreement
are solely for the purpose of reference, are not part of the agreement of the
parties and shall not in any way affect the meaning or interpretation of this
Agreement. Whenever any words are used herein in the masculine gender, they
shall be construed as though they were also used in the feminine gender in all
cases where they would so apply.

         9.8 GOVERNING LAW. This Agreement shall be governed by and construed
and enforced in accordance with the laws of the State of New York (regardless of
the laws that might otherwise govern under applicable principles of conflicts
law) as to all matters, including, without limitation, matters of validity,
construction, effect, performance and remedies.

         9.9 COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

         9.10 LEGAL ENFORCEABILITY. Any provision of this Agreement which is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof. Any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.


         9.11 NO THIRD PARTY BENEFICIARIES. This Agreement is solely for the
benefit of Reuters, the Reuters Affiliates, Instinet and the Instinet
Affiliates, and is not intended to confer upon any other person any rights or
remedies hereunder.


         9.12 JURISDICTION; FORUM.

                  (a) By the execution and delivery of this Agreement, Reuters
and Instinet submit and agree to cause the Reuters Affiliates and Instinet
Affiliates, respectively, to


                                       22
<PAGE>   26
submit to the personal jurisdiction of any state or federal court in the State
of New York in any suit or proceeding arising out of or relating to this
Agreement.

                  (b) To the extent that Reuters, Instinet, any Reuters
Affiliate or any Instinet Affiliate has or hereafter may acquire any immunity
from jurisdiction of any New York court or from any legal process (whether
through service or notice, attachment prior to judgment, attachment in aid of
execution, execution or otherwise) with respect to itself or its property,
Reuters or Instinet, as the case may be, hereby irrevocably waives, and agrees
to cause the Reuters Affiliates and the Instinet Affiliates, respectively, to
waive such immunity in respect of its obligations with respect to this
Agreement.

                  (c) The parties hereto agree that an appropriate and
convenient, non-exclusive forum for any disputes between any of the parties
hereto or the Reuters Affiliates and the Instinet Affiliates arising out of this
Agreement shall be in any state or federal court in the State of New York.

         9.13 AMENDMENT AND MODIFICATION. This Agreement may be amended,
modified or supplemented only by written agreement of the parties.

                  IN WITNESS WHEREOF, each of the parties hereto has caused this
Agreement to be executed by a duly authorized officer as of the date first above
written.

                                    REUTERS AMERICA HOLDINGS, INC.

                                    By:
                                       ------------------------------------
                                    Name:
                                    Title:

                                    INSTINET GROUP, LLC

                                    By:
                                       ------------------------------------
                                    Name:
                                    Title:

                                    INSTINET GLOBAL HOLDINGS, INC.

                                    By:
                                       ------------------------------------
                                    Name:
                                    Title:





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