<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION
                       ----------------------------------

                             WASHINGTON, D.C. 20549
                             ----------------------

                                   FORM 10-Q/A
                                   -----------

                  QUARTERLY REPORT UNDER SECTION 13 OR 15(d) OF

                       THE SECURITIES EXCHANGE ACT OF 1934


      For the Quarter Ended September 30, 1998 Commission File No. 1-12811


                            U.S.B. HOLDING CO., INC.
                            ------------------------
             (Exact name of registrant as specified in its charter)

                  DELAWARE                           36-3197969
                  --------                           ----------
         (State or other jurisdiction of         (I.R.S. Employer
            incorporation or organization)       Identification No.)


                 100 DUTCH HILL ROAD, ORANGEBURG, NEW YORK 10962
                 -----------------------------------------------
             (Address of principal executive office with zip code)

                                  914-365-4600
                                  ------------
               (Registrant's telephone number including area code)


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months and (2) has been subject to such filing requirements for
the past 90 days.


                             YES    /X/           NO


Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practicable date.

<TABLE>
<CAPTION>
                CLASS                   OUTSTANDING AT NOVEMBER 4, 1998
                -----                   -------------------------------
        <S>                             <C>
        Common stock, par value
               $0.01 per share                     14,392,513
</TABLE>


<PAGE>




        FORM 10Q/A FOR THE QUARTER ENDED SEPTEMBER 30, 1998 INCLUDES A RESTATED
FINANCIAL DATA SCHEDULE (EXHIBIT 27) WITH PRIOR PERIOD INFORMATION RELATING TO
THE ACQUISITION OF TAPPAN ZEE FINANCIAL, INC. BY U.S.B. HOLDING CO., INC., WHICH
WAS COMPLETED ON AUGUST 31, 1998.



                                       1

<PAGE>


                           PART II - OTHER INFORMATION

U.S.B. HOLDING CO., INC.

<TABLE>
<CAPTION>

ITEM 6.         EXHIBITS AND REPORTS ON FORM 8-K
-------         --------------------------------
<S>             <C>
(A)   Exhibits

Exhibit No.     Exhibit
-----------     -------

(3)(a)          Amended and restated Certificate of Incorporation, as amended,
                of Registrant (incorporated herein by reference to Registrant's
                Quarterly Report on Form 10-Q for the quarter ended June 30,
                1998, Exhibit (3)(a)).

(3)(b)          Bylaws of Registrant (incorporated herein by reference from
                Registrant's Registration Statement on Form S-14 (file no.
                2-79734), Exhibit 3(b)).

(4)(a)          Junior Subordinated Indenture, dated February 5, 1997, between
                Registrant and The Chase Manhattan Bank, as trustee
                (incorporated herein by reference to Registrant's Annual Report
                on Form 10-K for the year ended December 31, 1996 ("1996 10-K"),
                Exhibit (4)(a)).

(4)(b)          Guarantee Agreement, dated February 5, 1997, by and between
                Registrant and The Chase Manhattan Bank, as trustee for the
                holders of 9.58% Capital Securities of Union State Capital Trust
                I (incorporated herein by reference to Registrant's 1996 10-K,
                Exhibit (4)(b)).

(4)(c)          Amended and Restated Declaration of Trust of Union State Capital
                Trust I (incorporated herein by reference to Registrant's 1996
                10-K, Exhibit (4)(c)).

(10)(a)         Agreement of Employment dated as of July 1, 1994 between the
                Company and the Bank and Thomas E. Hales (incorporated herein by
                reference to Registrant's Annual Report on Form 10-K for the
                year ended December 31, 1994, Exhibit (10)(a)).

(10)(b)         Registrant's 1984 Incentive Stock Option Plan (incorporated
                herein by reference from Form S-8 Registration Statement, file
                No. 2-90674, Exhibit 28 (b)).

(10)(c)         Registrant's 1993 Incentive Stock Option Plan (incorporated
                herein by reference from Registrant's Annual Report on Form 10-K
                for the year ended December 31, 1993 ("1993 10-K"), Exhibit
                (10)(c)).

(10)(d)         Registrant's Employee Stock Ownership Plan (With Code Section
                401(k) Provisions) (incorporated herein by reference from
                Registrant's 1993 10-K, Exhibit (10)(d)).

</TABLE>

                                       2

<PAGE>


<TABLE>
<CAPTION>

ITEM 6.         EXHIBITS AND REPORTS ON FORM 8-K
-------         --------------------------------
<S>             <C>
(A)   Exhibits

Exhibit No.     Exhibit
-----------     -------

(10)(e)         Registrant's Dividend Reinvestment and Stock Purchase Plan
                (incorporated herein by reference from Registrant's Form S-3
                Registration Statement, file No. 33-72788).

(10)(f)         Registrant's Director Stock Option Plan (incorporated herein by
                reference to Registrant's 1996 10-K, Exhibit (10)(f)).

(10)(g)         Registrant's Key Employees' Supplemental Investment Plan, as
                amended July 1, 1997 (incorporated herein by reference to
                Registrant's Form 11-K for the year ended December 31, 1996).

(10)(h)         Purchase Agreement, dated January 31, 1997, by and among
                Registrant, Union State Capital Trust I and Keefe, Bruyette &
                Woods, Inc. (incorporated herein by reference to Registrant's
                1996 10-K, Exhibit (10)(h)).

(10)(i)         Registration Rights Agreement, dated February 5, 1997, by and
                among Registrant, Union State Capital Trust I and Keefe,
                Bruyette & Woods, Inc. (incorporated herein by reference to
                Registrant's 1996 10-K, Exhibit (10)(i)).

(10)(j)         Registrant's 1997 Employee Stock Option Plan (incorporated
                herein by reference to Registrant's proxy statement filed April
                18, 1997).

(10)(k)         Agreement and Plan of Merger, dated as of March 6, 1998, between
                U.S.B. Holding Co., Inc. and Tappan Zee Financial, Inc.
                (incorporated herein by reference to Registrant's Current Report
                on Form 8-K dated as of March 6, 1998).

(10)(l)         Stock Option Agreement, dated as of March 6, 1998, between
                U.S.B. Holding Co., Inc. and Tappan Zee Financial, Inc.
                (incorporated herein by reference to Registrant's Current Report
                on Form 8-K dated as of March 6, 1998).

(10)(m)         Registrant's 1998 Director Stock Option Plan (incorporated
                herein by reference from Registrant's Registration Statement on
                Form S-8 filed June 5, 1998, Exhibit (10)(d)).

(10)(n)         Tappan Zee Financial, Inc. 1996 Stock Option Plan for Officers
                and Employees ("Employee Option Plan") (incorporated herein by
                reference to Exhibit A to Tappan Zee Financial, Inc.'s Proxy
                Statement for use in connection with its 1996 Annual Meeting of
                Shareholders (the "Tappan Zee 1996 Proxy Statement").

(10)(o)         Amendment No. 1 to the Employee Option Plan (incorporated herein
                by reference to Tappan Zee Financial, Inc.'s Annual Report on
                Form 10-K for the fiscal year ended March 31, 1997 (the "Tappan
                Zee 1997 10-K"), Exhibit 10.1.1).

</TABLE>

                                       3

<PAGE>
<TABLE>
<CAPTION>

ITEM 6.         EXHIBITS AND REPORTS ON FORM 8-K
-------         --------------------------------
<S>             <C>
(A)   Exhibits

Exhibit No.     Exhibit
-----------     -------

(10)(p)         Amendment No. 2 to the Employee Option Plan (incorporated herein
                by reference to Exhibit A to Tappan Zee Financial, Inc.'s Proxy
                Statement for use in connection with its 1997 Annual Meeting of
                Shareholders (the " Tappan Zee 1997 Proxy Statement").

(10)(q)         Tappan Zee Financial, Inc. 1996 Stock Option Plan for Outside
                Directors ("Outside Director Option Plan") (incorporated herein
                by reference to Exhibit B to the Tappan Zee 1996 Proxy
                Statement).

(10)(r)         Amendment No. 1 to the Outside Director Option Plan
                (incorporated herein by reference to the Tappan Zee 1997 10-K,
                Exhibit 10.2.1).

(10)(s)         Amendment No. 2 to the Outside Director Option Plan
                (incorporated herein by reference to Exhibit B to the Tappan Zee
                1997 Proxy Statement).

(10)(t)         Tappan Zee Financial, Inc. 1996 Recognition and Retention Plan
                for Officers and Employees ("Employee RRP") (incorporated herein
                by reference to Exhibit C to the Tappan Zee 1996 Proxy
                Statement).

(10)(u)         Amendment No. 1 to the Employee RRP (incorporated herein by
                reference to the Tappan Zee 1997 10-K, Exhibit 10.3.1 ).

(10)(v)         Amendment No. 2 to the Employee RRP (incorporated herein by
                reference to Exhibit C to the Tappan Zee 1997 Proxy Statement).

(10)(w)         Tappan Zee Financial, Inc. 1996 Recognition and Retention Plan
                for Outside Directors ("Outside Director RRP") (incorporated
                herein by reference to Exhibit D to the Tappan Zee 1996 Proxy
                Statement).

(10)(x)         Amendment No. 1 to the Outside Director RRP (incorporated herein
                by reference to the Tappan Zee 1997 10-K, Exhibit 10.4.1).

(10)(y)         Amendment No. 2 to the Outside Director RRP (incorporated herein
                by reference to Exhibit D to the Tappan Zee 1997 Proxy
                Statement).

(10)(z)         Employee Stock Ownership Plan of Tappan Zee Financial, Inc. and
                Certain Affiliates, as amended (incorporated herein by reference
                to Tappan Zee Financial Inc.'s Annual Report on Form 10-K for
                the fiscal year ended March 31, 1996 (the "Tappan Zee 1996
                10-K"), Exhibit 10.6).

(10)(aa)        Loan Agreement to the Employee Stock Ownership Plan Trust of
                Tappan Zee Financial, Inc. and Certain Affiliates (incorporated
                herein by reference to the Tappan Zee 1996 10-K, Exhibit 10.7).

</TABLE>

                                       4

<PAGE>

<TABLE>
<CAPTION>

ITEM 6.         EXHIBITS AND REPORTS ON FORM 8-K
-------         --------------------------------
<S>             <C>
(A)   Exhibits

Exhibit No.     Exhibit
-----------     -------

(10)(bb)        Tarrytowns Bank Deferred Compensation Plan for Directors of
                Tarrytowns Bank, FSB (Incorporated herein by reference to the
                Registration Statement on Form S-1, No. 33-94128, filed on June
                30, 1995, as amended (the "Tappan Zee Registration Statement"),
                Exhibit 10.7).

(10)(cc)        Retirement Plan for Board Members of Tappan Zee Financial, Inc.
                and Certain Affiliates, adopted effective as of October 5, 1995
                (incorporated herein by reference to the 1996 10-K, Exhibit
                10.9).

(10)(dd)        Consulting Agreement by and between Tarrytowns Bank, FSB and
                Stephen C. Byelick, dated effective as of August 31, 1998.*

(10)(ee)        Employment Agreement by and between Tarrytowns Bank, FSB and
                Harry G. Murphy, dated effective as of August 31, 1998.*

(10)(ff)        Employee Retention Agreement by and among Tappan Zee Financial,
                Inc. Tarrytowns Bank, FSB and Christina Vidal, effective as of
                October 5, 1995 (incorporated herein by reference to the 1996
                10-K, Exhibit 10.15).

(10)(gg)        Employee Retention Agreement by and among Tappan Zee Financial,
                Inc., Tarrytowns Bank, FSB and Margaret E. Sampson, effective as
                of October 5, 1995 (incorporated herein by reference to the
                Tappan Zee 1996 10-K, Exhibit 10.16).

(10)(hh)        Employee Retention Agreement by and among Tappan Zee Financial,
                Inc., Tarrytowns Bank, FSB and Valerie Wilson, effective as of
                October 5, 1995 (incorporated herein by reference to the Tappan
                Zee 1996 10-K, Exhibit 10.17).

(10)(ii)        Forms of Stock Option Agreement by and between Tappan Zee
                Financial, Inc. and recipients of stock options granted pursuant
                to the Employee Option Plan and the Outside Director Option Plan
                (incorporated herein by reference to the Tappan Zee 199710-K,
                Exhibit 10.16).

(10)(jj)        Forms of Restricted Stock Award Notices to award recipients,
                pursuant to the Employee RRP and the Outside Director RRP
                (incorporated herein by reference to the Tappan Zee 1997 10-K,
                Exhibit 10.17).

(11)            Computation of earnings per share.*

(27)            Financial Data Schedule.**

</TABLE>

*       Previously filed with Form 10-Q on November 13, 1998.
**      Filed Herewith.


                                       5

<PAGE>

<TABLE>
<CAPTION>

ITEM 6.         EXHIBITS AND REPORTS ON FORM 8-K
-------         --------------------------------
<S>             <C>

(B)     Reports on Form 8-K

                The following reports on Form 8-K were filed during the quarter
                ended September 30, 1998:

                - Current report on Form 8-K dated as of July 16, 1998 reported
                  under item 5, "Other Events," that the Company issued a 
                  press release reporting certain operating results for the 
                  Company for the quarter ended June 30, 1998.

                - Current reports on Form 8-K dated as of August 19 and 20, 1998
                  reported under item 5, "Other Events," that the Company 
                  issued a press release on August 19, 1998 reporting that it 
                  had received approval for its acquisition of Tappan Zee 
                  Financial, Inc. from the Board of Governors of the Federal 
                  Reserve Bank, and issued a press release on August 20, 1998 
                  reporting that it received approval for the acquisition by 
                  the Office of Thrift Supervision and by the shareholders of 
                  Tappan Zee.

                - Current report on Form 8-K dated as of August 31, 1998
                  reported under Item 5, "Other Events," that a press release
                  was issued announcing that the Company had completed its
                  acquisition of Tappan Zee Financial, Inc.

</TABLE>
                                   SIGNATURES

Pursuant to the requirements of the Securities and Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized, on January 22, 1999.

                            U.S.B. HOLDING CO., INC.



/s/ Thomas E. Hales                             /s/ Steven T. Sabatini   
------------------------------------            -------------------------------
Thomas E. Hales                                 Steven T. Sabatini
Chairman of the Board, President,               Senior Executive Vice President,
Chief Executive Officer and Director            Chief Financial Officer and
                                                Assistant Secretary
                                                (Principal Financial and 
                                                  Accounting Officer)


                                       6