Exhibit 4.1


 


NUMBER OF UNITS


 


U-              


 


SEE REVERSE FOR CERTAIN DEFINITIONS


 


CUSIP [--]


 


BILANDER ACQUISITION CORP.



UNITS CONSISTING OF ONE SHARE OF CLASS A COMMON STOCK AND

ONE-FOURTH OF ONE REDEEMABLE WARRANT, EACH WHOLE WARRANT ENTITLING THE HOLDER TO PURCHASE ONE SHARE OF

CLASS A COMMON STOCK


 


THIS CERTIFIES THAT is the owner of Units.


 


Each Unit (“Unit”) consists
of one (1) share of Class A common stock, par value $0.0001 per share (“Common Stock”), of Bilander Acquisition Corp.,
a Delaware corporation (the “Company”), and one-fourth (1/4) of one warrant (each whole warrant, a “Warrant”).
Each whole Warrant entitles the holder to purchase one (1) share (subject to adjustment) of Common Stock for $11.50 per share (subject
to adjustment). Only whole Warrants are exercisable. Each whole Warrant will become exercisable on the later of (i) thirty (30) days after
the Company’s completion of a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or other similar
business combination with one or more businesses (each a “Business Combination”), or (ii) twelve (12) months from the
closing of the Company’s initial public offering, and will expire unless exercised before 5:00 p.m., New York City Time, on the
date that is five (5) years after the date on which the Company completes its initial Business Combination, or earlier upon redemption
or liquidation (the “Expiration Date”). The Common Stock and Warrants comprising the Units represented by this certificate
are not transferable separately prior to     , 2021, unless Morgan Stanley & Co. LLC, Deutsche Bank Securities
Inc. and Evercore Group L.L.C. elect to allow earlier separate trading, subject to the Company’s filing of a Current Report on Form
8-K with the Securities and Exchange Commission containing an audited balance sheet reflecting the Company’s receipt of the gross
proceeds of the Company’s initial public offering and issuing a press release announcing when separate trading will begin. No fractional
Warrants will be issued upon separation of the Units. The terms of the Warrants are governed by a Warrant Agreement, dated as of     ,
2021, between the Company and American Stock Transfer & Trust Company, LLC, as Warrant Agent, and are subject to the terms and provisions
contained therein, all of which terms and provisions the holder of this certificate consents to by acceptance hereof. Copies of the Warrant
Agreement are on file at the office of the Warrant Agent at 6201 15th Avenue, Brooklyn, NY 11219, and are available to any Warrant holder
on written request and without cost.


 


This certificate is not valid unless countersigned
by the Transfer Agent and registered by the Registrar of the Company.


 


This certificate shall be governed by and construed
in accordance with the internal laws of the State of New York.


 


Witness the facsimile signature of its duly authorized
officers.


 


	Chief Executive Officer	 	Chief Financial Officer




     


     


    

Bilander Acquisition Corp.


 


The Company will furnish without charge to each
unitholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional or other special
rights of each class of stock or series thereof of the Company and the qualifications, limitations, or restrictions of such preferences
and/or rights.


 


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


 


	TEN COM	—	as tenants in common	UNIF GIFT MIN ACT —	Custodian
	 	 	 	 	 	 	 
	TEN ENT	—	as tenants by the entireties	 	(Cust)	 	(Minor)
	 	 	 	 	 
	JT TEN	—	as joint tenants with right of survivorship and not as tenants in common	 	
    under Uniform Gifts to Minors Act

    

    (State)

     



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


 


For value received, hereby sell, assign and transfer unto


 


PLEASE INSERT SOCIAL SECURITY OR





OTHER





IDENTIFYING NUMBER OF ASSIGNEE


 


(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING
ZIP CODE, OF ASSIGNEE)


 


Units represented by the within Certificate, and do hereby irrevocably
constitute and appoint


 


Attorney to transfer the said Units on the books of the within named
Company with full power of substitution in the premises.


 


Dated


 


	 	Notice: The signature to this assignment must correspond with the name as written upon the face of the certificate in every particular, without alteration or enlargement or any change whatever.


 


Signature(s) Guaranteed:


 


THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION
(BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM,
PURSUANT TO S.E.C. RULE 17Ad-15 (OR ANY SUCCESSOR RULE).


 


  


 


In each case, as more fully described in the Company’s final
prospectus dated     , 2021, the holder(s) of the Company’s Class A common stock shall be entitled to receive
a pro-rata portion of certain funds held in the trust account established in connection with the Company’s initial public offering
only in the event that (i) the Company redeems the shares of Class A common stock sold in its initial public offering and liquidates because
it does not consummate an initial business combination by       , 2023 (or such later date if such period
is extended pursuant to the Company’s Certificate of Incorporation as in effect at such time), (ii) the Company redeems the shares
of Class


 

 




     


     


    

A common stock sold in its initial public offering in connection with
a stockholder vote to amend the Company’s amended and restated certificate of incorporation to modify the substance or timing of
the Company’s obligation to redeem 100% of the Class A common stock if it does not consummate an initial business combination by
     , 2023 (or such later date, if such period is extended pursuant to the Company’s Certificate of Incorporation
as in effect at such time) or with respect to any other material provisions relating to stockholders’ rights of pre-initial business
combination activity, or (iii) if the holder(s) seek(s) to redeem for cash his, her or its respective shares of Class A common stock in
connection with a tender offer (or proxy solicitation, solely in the event the Company seeks stockholder approval of the proposed initial
business combination) setting forth the details of a proposed initial business combination. In no other circumstances shall the holder(s)
have any right or interest of any kind in or to the trust account.