<PAGE>   1


                                                                    Exhibit 4(f)

                                SPECIAL AMENDMENT
                                     TO THE
                         STATE AUTO INSURANCE COMPANIES
                            CAPITAL ACCUMULATION PLAN


                                   BACKGROUND


A.   State Automobile Mutual Insurance Company, State Auto Property and Casualty
     Insurance Company and other related employers (collectively, the "Company")
     maintain the State Auto Insurance Companies Capital Accumulation Plan (the
     "Plan") for the benefit of their employees and their beneficiaries.

B.   The Company desires to amend the Plan to add State Auto Financial
     Corporation Stock as an available investment option under the Plan.

C.   Section 14.01 of the Plan permits the Company to amend the Plan at any
     time.


                                    AMENDMENT


     The provisions of this Special Amendment shall be generally effective as of
March 1, 2001, unless another date is specifically provided herein.

1.   A new Section 1.42 of the Plan is hereby added to read as follows, with all
     subsequent sections renumbered sequentially:

     1.42 SHARES

          The no par value common shares of State Auto Financial Corporation, an
          Ohio Corporation.

2.   A new Section 4.03 of the Plan is hereby added to read as follows:

     4.03 INVESTMENT FUNDS

          The Committee and the Trustee shall establish certain Investment
          Funds, rules governing the administration of the Investment Funds, and
          procedures for directing the investment of Participant Accounts among
          the Investment Funds. The Trustee shall invest and reinvest the
          principal and income of each Account in the Trust Fund as required by
          ERISA and as directed by Participants. The Committee and the Company
          reserve the right to change the investment options
<PAGE>   2

          available under the Plan and the rules governing investment
          designations at any time and from time to time.

          Effective March 1, 2001, the Trustee is specifically authorized to
          maintain the State Auto Financial Corporation Common Stock Fund ("STFC
          Stock Fund") as one of the Investment Funds. The STFC Stock Fund shall
          consist of Shares and cash or cash equivalents needed to meet
          obligations of such fund or for the purchase of Shares. One of the
          purposes of the Plan is to provide Participants with ownership
          interests in an affiliate of the Company. To the extent practicable,
          all available assets of the STFC Stock Fund shall be used to purchase
          Shares, which shall be held by the Trustee and allocated to
          Participant Accounts until distributed in-kind or sold for
          distribution of cash to Participants or Beneficiaries or until
          disposition is required to implement changes in investment
          designations.


          The Trustee may acquire or dispose of Shares as necessary to implement
          Participant directions and may net transactions within the Trust Fund.
          In addition, when acquiring Shares, the Trustee may acquire Shares
          directly from State Auto Financial Corporation ("STFC"), the Company
          or on the open market as necessary to effect Participant directions.
          In any case, the price paid for such Shares shall not exceed the fair
          market value of the Shares. The fair market value of the Shares
          acquired directly from STFC or the Company shall mean the mean between
          the high and low bid and ask prices as reported by the NASDQ National
          Market on the date of such transaction.


          In no event, however, shall Participants be permitted to direct that
          their Accounts and/or any additional contributions to the Plan be
          invested in the STFC Stock Fund until the Company, the Plan, the
          Trustee and all other relevant parties have fully complied with such
          requirements, including, but not limited to, federal and state
          securities laws, as the Committee has determined to be applicable. The
          Committee may restrict the ability of any person covered under Section
          16 of the Securities Exchange Act of 1934, as amended, or any other
          corporate insider of the Company to direct the investment of his
          Account in the STFC Stock Fund. Notwithstanding any provision to the
          contrary, the Committee, may, in its sole discretion and where the
          terms of any relevant investment contract, regulated investment
          company or pooled or group trust so require, impose special terms,
          conditions and restrictions upon a Participant's right to direct the
          investment in, or transfer into or out of, such contracts, companies
          or trusts.


          Each Investment Fund (other than the STFC Stock Fund) shall be
          established by the Trustee at the direction or with the concurrence of
          the Committee. Investment Funds may, as so determined, consist of
          preferred and common stocks, bonds, debentures, negotiable instruments
          and evidences of indebtedness of every kind and form, or in securities
          and units of participation issued by companies registered under the
          Investment Companies Act of 1940, master limited

<PAGE>   3

          partnerships or real estate investment trusts, or in any common or
          collective fund established or maintained for the collective
          investment and reinvestment of assets of pension and profit sharing
          trusts which are exempt from federal income taxation under the Code,
          or any combination of the foregoing. The Trustee shall hold, manage,
          administer, invest, reinvest, account for and otherwise deal with the
          Trust Fund and each separate Investment Fund as provided in the Trust
          Agreement.


          Anything in the Plan or Trust Agreement to the contrary
          notwithstanding, the Trustee shall not sell, alienate, encumber,
          pledge, transfer or otherwise dispose of, or tender or withdraw, any
          Shares held by it under the Trust Agreement, except (i) as
          specifically provided for in the Plan or (ii) in the case of a "TENDER
          OFFER" as directed in writing by a Participant (or Beneficiary, where
          applicable) on a form provided or approved by the Committee and
          delivered to the Trustee. For the purposes hereof, a Tender Offer
          shall mean any offer for, or request for or invitation for tenders of,
          or offer to purchase or acquire, any Shares that is directed generally
          to shareholders of STFC or any transaction which may be defined as a
          Tender Offer under rules or regulations promulgated by the Securities
          and Exchange Commission. To the extent that any money or other
          property is received by the Trustee as a result of a tender of Shares
          not prohibited by the preceding sentence, such money or property shall
          be allocated to such other Investment Fund(s) as directed by the
          Participants in whose Account the Shares so tendered were held.


3.   Section 7.01(c) of the Plan is hereby amended in its entirety to read as
     follows:

          (c)  For Participants terminating on or after January 1, 1986, payment
               shall be made in cash or, effective March 1, 2001, in Shares, if
               applicable, in accordance with method (i) of Section 7.01(b) to a
               Participant or former Participant who terminates employment for
               any reason.

4.   A new Section 12.08 of the Plan is hereby added to read as follows:

     12.08 REGISTRATION AND VOTING OF SHARES

          All Shares acquired by the Trustee shall be held in the possession of
          the Trustee until disposed of pursuant to the provisions of the Plan
          or the Trust Agreement. Such Shares may be registered in the name of
          the Trustee or its nominee. Before each annual or special meeting of
          the shareholders of STFC, the Trustee shall send to each Participant a
          copy of the proxy solicitation material therefor, together with a form
          requesting confidential instructions to the Trustee on how to vote the
          Shares credited to his Account. Upon receipt of such instructions the
          Trustee shall vote the Shares as instructed. Any Shares held in
          Participants' Accounts as to which the Trustee does not receive
          instructions shall not be voted. Except as otherwise required by law,
          the Trustee shall vote that number of Shares not

<PAGE>   4

          credited to Participants' Accounts in the same proportion on each
          issue as it votes those Shares credited to Participants' Accounts for
          which it received voting instructions from Participants.

5.   All other provisions of the Plan shall remain in full force and effect.



                             STATE AUTOMOBILE MUTUAL
                                INSURANCE COMPANY

                             BY: /s/ Robert H. Moone
                                 ----------------------------------------
                             TITLE: President and Chief Executive Officer
                                   --------------------------------------
                             DATE:  February __, 2001
                                   --------------------------------------


                             STATE AUTO PROPERTY AND CASUALTY INSURANCE COMPANY

                             BY: /s/Robert H. Moone
                                 ----------------------------------------
                             TITLE: President and Chief Executive Officer
                                   --------------------------------------
                             DATE:  February __, 2001
                                   --------------------------------------