FirstMark Horizon Acquisition Corp. New York, NY 10011

Exhibit 10.4

EXECUTION VERSION

FirstMark Horizon Acquisition Corp.

000 0^xx Xxx, 0^xx Xxxxx

Xxx Xxxx, XX 00000

October 5, 2020

FirstMark Capital LLC

000 0xx Xxx, 0xx Xxxxx

Xxx Xxxx, XX 00000

Re: Administrative Services Agreement

Gentlemen:

This letter agreement by and between FirstMark Horizon Acquisition Corp., a Delaware corporation (the “Company”), and FirstMark Capital LLC, a Delaware limited liability company (“FirstMark”), dated as of the date hereof, will confirm our agreement that, commencing on the date the securities of the Company are first listed on the New York Stock Exchange (the “Listing Date”) and continuing until the earlier of the consummation by the Company of an initial business combination and the Company’s liquidation (in each case as described in the Registration Statement on Form S-1 (File No. 333-248916) filed with the Securities and Exchange Commission) (such earlier date hereinafter referred to as the “Termination Date”):

1. FirstMark shall make available to the Company, at 000 0^xx Xxx, 0^xx Xxxxx, Xxx Xxxx, XX 00000 (or any successor location or other existing office locations of FirstMark or any of its affiliates), certain office space, administrative and support services, including compliance services, as may be reasonably requested by the Company. In exchange therefor, the Company shall pay, on the first day of each month, FirstMark the sum of $10,000 per month commencing on the Listing Date and continuing monthly thereafter until the Termination Date; and

2. FirstMark hereby irrevocably waives any and all right, title, interest, causes of action and claims of any kind or nature whatsoever (each, a “Claim”) in or to, and any and all right to seek payment of any amounts due to it out of, the trust account established for the benefit of the public stockholders of the Company and into which substantially all of the proceeds of the Company’s initial public offering will be deposited (the “Trust Account”), and hereby irrevocably waives any Claim it presently has or may have in the future as a result of, or arising out of, this letter agreement, which Claim would reduce, encumber or otherwise adversely affect the Trust Account or any monies or other assets in the Trust Account, and further agrees not to seek recourse, reimbursement, payment or satisfaction of any Claim against the Trust Account or any monies or other assets in the Trust Account for any reason whatsoever.

This letter agreement constitutes the entire agreement and understanding of the parties hereto in respect of its subject matter and supersedes all prior understandings, agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter hereof or the transactions contemplated hereby.

This letter agreement may not be amended, modified or waived as to any particular provision, except by a written instrument executed by all parties hereto.

No party hereto may assign either this letter agreement or any of its rights, interests, or obligations hereunder without the prior written approval of the other party, provided that FirstMark may assign this letter agreement to an affiliate without the prior written approval of the Company. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or title to the purported assignee.

This letter agreement, the entire relationship of the parties hereto, and any litigation between the parties (whether grounded in contract, tort, statute, law or equity) shall be governed by and construed in accordance with the laws of the State of New York.

This letter agreement may be executed in one or more counterparts, each of which shall for all purposes be deemed to be an original but all of which together shall constitute one and the same letter agreement.

[Signature page follows]

	Very truly yours,
	FIRSTMARK HORIZON ACQUISITION CORP.
	By:	/s/ Xxxx Xxxxxx
		Name:	Xxxx Xxxxxx
		Title:	Secretary

AGREED TO AND ACCEPTED BY:
FirstMark Capital LLC
By:	/s/ Xxxxxxx Xxxxxxxxx
	Name:	Xxxxxxx Xxxxxxxxx
	Title:	Authorized Signatory

[Signature Page to Administrative Services Agreement]