<PAGE>   1
                                                                     EXHIBIT 4.1



     UNLESS THIS SECURITY (AS DEFINED HEREIN) IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (THE
"DEPOSITARY") TO THE COMPANY (AS DEFINED HEREIN) OR ITS AGENT FOR REGISTRATION
OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE TO BE ISSUED IS REGISTERED
IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITARY AND ANY AMOUNT PAYABLE THEREUNDER IS MADE
PAYABLE TO CEDE & CO. OR TO SUCH OTHER NAME, ANY TRANSFER, PLEDGE OR OTHER USE
HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE
REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

     UNLESS AND UNTIL THIS SECURITY IS EXCHANGED IN WHOLE OR IN PART FOR
CERTIFICATED SECURITIES REGISTERED IN THE NAMES OF THE VARIOUS BENEFICIAL
HOLDERS HEREOF AS THEN CERTIFIED TO THE COMPANY BY THE DEPOSITARY OR A SUCCESSOR
DEPOSITARY, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE
DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO
THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY
SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR
DEPOSITARY.

                             WASHINGTON MUTUAL, INC.

                        ____% SENIOR NOTES DUE _________

No. 1                                                                $__________
                                                                          CUSIP:

     WASHINGTON MUTUAL, INC., a Washington corporation (hereinafter called the
"Company," which term shall refer to such Company until a successor corporation
shall have become such pursuant to the provisions of the Indenture referred to
herein and thereafter "Company" shall mean such successor corporation), for
value received, hereby promises to pay to Cede & Co., or registered assigns, the
principal sum of ____________________ ($_______) on ___________, and to pay
interest thereon from ___________, or from the most recent Interest Payment Date
to which interest has been paid or duly provided for, semiannually on _________
and _________ in each year,

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commencing __________, at the rate of ____% per annum, until the principal
hereof is paid or made available for payment.

     The interest so payable, and punctually paid or duly provided for, on any
Interest Payment Date will, as provided in such Indenture, be paid to the Person
in whose name this Security (or one or more Predecessor Securities) is
registered at the close of business on the Regular Record Date for such
interest, which shall be (in each case whether or not a Business Day) the ______
or ______ as the case may be, next preceding such Interest Payment Date. Any
interest not punctually paid or duly provided for shall forthwith cease to be
payable to the Holder on such Regular Record Date and may either be paid to the
Person in whose name this Security (or one or more Predecessor Securities) is
registered at the close of business on a Special Record Date for the payment of
such Defaulted Interest to be fixed by the Trustee, notice whereof shall be
given to Holders of Securities of this series not less than 10 days prior to
such Special Record Date, or be paid at any time in any other lawful manner not
inconsistent with the requirements of any securities exchange on which the
Securities of this series may be listed, and upon such notice as may be required
by such exchange, all as more fully provided in said Indenture.

     Payment of the principal of (and premium, if any, on) and interest on this
Security will be made at the office or agency of the Company maintained for that
purpose in the Borough of Manhattan, in The City of New York, in such coin or
currency of the United States of America as at the time of payment is legal
tender for payment of public and private debts; provided, however, that at the
option of the Company, payment of interest may be made by check mailed to the
address of the Person entitled thereto as such address shall appear in the
Security Register.

     This security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of ______ ___, 200_ (herein called the
"Indenture"), between the Company and Harris Trust and Savings Bank, as Trustee
(herein called the "Trustee," which term includes any successor trustee or
trustees under the Indenture), to which Indenture and all indentures
supplemental thereto reference is hereby made for a statement of the respective
rights, limitations of rights, duties and immunities thereunder of the Company,
the Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered. This Security is one
of the series designated on the face hereof, limited in aggregate principal
amount to $_______.

     The Securities are not redeemable at the option of the Company prior to
Stated Maturity.

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     If an Event of Default with respect to Securities of this series shall
occur and be continuing, the principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture.

     The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each series to be
affected under the Indenture at any time by the Company and the Trustee with the
consent of the Holders of not less than a majority in principal amount of the
Securities at the time Outstanding of all series to be affected (acting as one
class). The indenture also provides that, regarding the Securities of any
series, the Holders of not less than a Majority in principal amount of the
Securities at the time outstanding of such series may waive certain past
defaults and their consequences on behalf of the Holders of all Securities of
such series. Any such consent or waiver by the Holder of this Security shall be
conclusive and binding upon such Holder and upon all future Holders of this
Security and of any Security issued upon the registration of transfer hereof or
in exchange hereof or in lieu hereof, whether or not notation of such consent or
waiver is made upon this Security.

     As provided in the Indenture, the Company shall be discharged from its
obligations with respect to the Securities of any series when (1) with respect
to all Outstanding Securities of such series, the Company has deposited or
caused to be deposited with the Trustee as a trust fund specifically pledged as
security for, and dedicated solely to, the benefit of the Holders of the
Securities of such series (i) money in an amount as will, or (ii) U.S.
Government Obligations as will, together with the predetermined and certain
income to accrue thereon without consideration of any reinvestment thereof, or
(iii) a combination of (i) and (ii) as will (in a written opinion with respect
to (ii) or (iii) of independent public accountants delivered to the Trustee), be
sufficient to pay and discharge the entire indebtedness on all Outstanding
Securities of such series for principal (and premium, if any) and interest, if
any, to the Stated Maturity; and (2) the Company has paid or caused to be paid
all other sums payable with respect to the Outstanding Securities of such
series; and (3) the Company has delivered to the Trustee an Officers'
Certificate and an Opinion of Counsel stating that all such conditions precedent
have been complied with; and (4) the Company has delivered to the Trustee (i) a
ruling directed to the Company and the Trustee from the United States Internal
Revenue Service to the effect that Holders of the Securities of such series will
not recognize income, gain or loss for Federal income tax purposes as a result
thereof and will be subject to Federal income tax as if such option had not been
exercised or (ii) an opinion of Counsel to the same effect and based upon a
change in law.

     No reference herein to the Indenture and no provisions of this Security or
of the Indenture shall alter or impair the obligation of the Company, which is
absolute and unconditional, to pay the principal of (and premium, if any) and
interest, if any, on this

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Security at the times, place and rate, and in the coin or currency, herein and
in the Indenture provided; subject, however, to the provisions for the discharge
of the Company from its obligations under the Securities upon satisfaction of
the conditions set forth in the preceding paragraph or in the Indenture.

     As provided in the Indenture, upon any consolidation or merger or any
conveyance, transfer or lease of the properties and assets of the Company
substantially as an entirety in accordance with the provisions of the Indenture,
the successor corporation formed by such consolidation or into which the
predecessor corporation is merged or to which such conveyance, transfer or lease
is made shall be substituted for the predecessor corporation with the same
effect as if such successor corporation had been named as the Company.
Thereafter the predecessor corporation shall be relieved of the performance and
observance of all obligations and covenants of the Indenture and the Securities,
including but not limited to the obligation to make payment of the principal of
(and premium, if any, on) and interest, if any, on all the Securities then
Outstanding, and, in the event of any such conveyance, transfer or lease, may be
liquidated and dissolved.

     As provided in the Indenture and subject to certain limitations therein set
forth, the transfer of this Security is registrable in the Security Register,
upon surrender of this Security for registration of transfer at the office or
agency of the Company in any place where the principal of (and premium, if any)
and interest on this Security are payable, when duly endorsed by, or accompanied
by a written instrument of transfer in form satisfactory to the Company and the
Security Registrar duly executed by, the Holder hereof or his attorney duly
authorized in writing, and thereupon one or more new Securities of this series,
of authorized denominations and for a like aggregate principal amount and tenor,
will be issued to the designated transferee or transferees.

     The Securities of this series are issuable only in registered form without
coupons in denominations of $1,000 and any larger amount that is an integral
multiple of $1,000. As provided in the Indenture and subject to certain
limitations therein set forth, Securities of this series are exchangeable for a
like aggregate principal amount and tenor of Securities of this series of a
different authorized denomination, upon surrender of the Securities to be
exchanged at any such office or agency.

     No service charge shall be made for any such registration of transfer or
exchange, but the Company may require payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     Prior to due presentment of this Security for registration of transfer, the
Company, the Trustee and any agent of the Company or the Trustee may treat the
Person in whose name this Security is registered as the owner hereof for all
purposes,

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whether or not this Security be overdue, and neither the Company, the Trustee
nor any such agent shall be affected by notice to the contrary.

     As provided in the Indenture, no recourse shall be had for the payment of
the principal of (or premium, if any, on) or the interest, if any, on this
Security, or any part hereof, or for any claim based hereon or otherwise in
respect hereof, or of the indebtedness represented hereby, or upon any
obligation, covenant or agreement of the Company in the Indenture, against any
incorporator, direct or indirect stockholder, officer or director, as such,
past, present or future, of the Company or of any successor corporation (either
directly or through the Company or any such successor corporation), whether by
virtue of any constitutional provision, statute or rule of law, or by the
enforcement of any assessment or penalty or otherwise, all liability, if any, of
that character against every such incorporator, stockholder, officer and
director being by the acceptance hereof, and as a condition of and as part of
the consideration for the issue hereof, expressly waived and released.

     The Indenture and the Securities shall be governed by and construed in
accordance with the laws of the State of New York.

     All terms used in this Security which are defined in the Indenture shall
have the meanings assigned to them in the Indenture.

     Unless the certificate of authentication hereon has been executed by the
Trustee by manual signature, this Security shall not be entitled to any benefit
under the Indenture or be valid or obligatory for any purpose.

     IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal.

                                        WASHINGTON MUTUAL, INC.


                                        By:
                                           -------------------------------------
                                                   Authorized Signatory

     [SEAL]

     Attest:



     --------------------------------
           Assistant Secretary

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                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

     This is one of the Securities of the series designated and issued under the
within mentioned Indenture.

     Dated: _______________, 200_


                                        HARRIS TRUST AND SAVINGS
                                        BANK, as Trustee


                                        By:
                                           -------------------------------------
                                                    Authorized Signatory

                                      -6-
<PAGE>   7

                                  ABBREVIATIONS

     The following abbreviations, when used in the inscription on this Security,
shall be construed as though they were written out in full according to
applicable laws or regulations.

<TABLE>
<S>       <C>                                        <C>
TEN COM - as tenants in common                       UNIF GIFT MIN ACT
TEN ENT - as tenants by the entireties with right
          of survivorship and not as tenants in
          common
JT TEN -  as joint tenants with right of                                  Custodian
          survivorship and not as tenants in         --------------------
          common                                     (Cust)

                                                     -------------------------------------
                                                      (Minor)
                                                      Under Uniform Gifts to Minor Act

                                                      ------------------------------------
                                                      (State)
</TABLE>


     Additional abbreviations may also be used though not in the above list.

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

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     FOR VALUE RECEIVED, the undersigned hereby sells, assigns and transfers to

     INSERT SOCIAL SECURITY OR
     OTHER IDENTIFYING NUMBER OF ASSIGNEE

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             PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS OF ASSIGNEE


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     the within Security of Washington Mutual, Inc., and irrevocably constitutes
and appoints to
                ----------------------------------------------------- transfer
said Security on the books of the within named Company, with full power
of substitution in the premises.

     Dated:
           --------------               ----------------------------------------

                                        ----------------------------------------
                                        The signature to this assignment must
                                        correspond with the name as written upon
                                        the face of the Security in every
                                        particular without alteration or
                                        enlargement, or any change whatsoever.

                                        Signatures must be guaranteed by an
                                        "eligible guarantor institution" meeting
                                        the requirements of the Security
                                        Registrar, which requirements include
                                        membership or participation in the
                                        Security Transfer Agent Medallion
                                        Program ("STAMP") or such other
                                        "signature guarantee program" as may be
                                        determined by the Security Registrar

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                                        in addition to, or in substitution for,
                                        STAMP, all in accordance with the
                                        Securities Exchange Act of 1934, as
                                        amended.

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