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As filed with the Securities and Exchange Commission on December 3, 2021

Registration Statement No. 333-259027

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 7

TO

FORM S-4

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

MCAP ACQUISITION CORPORATION*

(Exact Name of Registrant as Specified in Its Charter)

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311 South Wacker Drive, Suite 6400

Chicago, Illinois 60606

Telephone: (312) 258-8300

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Theodore L. Koenig

Chairman and Chief Executive Officer

311 South Wacker Drive, Suite 6400

Chicago, Illinois 60606

Telephone: (312) 258-8300

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent For Service)

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Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement becomes effective and on completion of the business combination described in the enclosed proxy statement/prospectus.

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If the securities being registered on this Form are to be offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ☐

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If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

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If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

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Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided to Section 7(a)(2)(B) of the Securities Act. ☐

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If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

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Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act, or until this Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

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PRELIMINARY PROXY STATEMENT/PROSPECTUS

SUBJECT TO COMPLETION, DATED DECEMBER 3, 2021

MCAP ACQUISITION CORPORATION

311 South Wacker Drive, Suite 6400

Chicago, Illinois 60606

Up to 60,813,148 shares of common stock

Dear MCAP Acquisition Corporation Stockholders:

On July 27, 2021, MCAP Acquisition Corporation, a Delaware corporation (“MCAP” or “Parent”), GRNT Merger Sub 1 LLC, a Delaware limited liability company (“Merger Sub 1”), GRNT Merger Sub 2 LLC, a Delaware limited liability company (“Merger Sub 2”), GRNT Merger Sub 3 LLC, a Delaware limited liability company (“Merger Sub 3”), GRNT Merger Sub 4 LLC, a Delaware limited liability company (“Merger Sub 4” and together with Merger Sub 1, Merger Sub 2 and Merger Sub 3, the “Merger Sub Entities”), H.I.G. Growth — AdTheorent Intermediate, LLC, a Delaware limited liability company (the “Blocker”), H.I.G. Growth — AdTheorent, LLC, a Delaware limited liability company (the “Blocker Member”), and AdTheorent Holding Company, LLC, a Delaware limited liability company (“AdTheorent” or the “Company”), entered into a business combination agreement (the “BCA”) pursuant to which, among other things, AdTheorent, the Blocker, and the Merger Sub Entities will engage in a series of four mergers (the “Mergers”), which will result in AdTheorent becoming a wholly owned subsidiary of Parent. The Mergers and the other transactions described in the BCA are collectively referred to herein as the “Business Combination.”

Upon the closing of the Business Combination (the “Closing”), each AdTheorent membership interest, issued and outstanding immediately prior to the Closing (including converted AdTheorent options and restricted stock units) will automatically be converted into and become the right to receive, in accordance with the Payment Spreadsheet (as defined in the BCA), its share of the aggregate transaction consideration set forth in the Payment Spreadsheet. Each unexercised option and restricted unit will automatically be converted into and become the right to receive, in accordance with the Payment Spreadsheet, its share of the aggregate transaction consideration set forth in the Payment Spreadsheet.

The aggregate transaction consideration to be paid in the Business Combination will be an amount equal to $775,000,000, minus certain consideration adjustments representing the obligations of the Company and which include (a) 50% of the total bonus amount to be paid to certain management employees in connection with the Business Combination, (b) the aggregate amount necessary to satisfy and discharge the Company’s obligations under the Monroe Credit Agreement (as defined in the BCA) immediately prior to the Closing, (c) an aggregate amount necessary to satisfy and discharge the Company’s obligations under the SVB Credit Agreement (as defined in the BCA) immediately prior to the Closing, (d) the aggregate amount necessary for the Company to terminate its sublease for the Company’s New York office and discharge all of its obligations thereunder immediately prior to the Closing, and (e) the aggregate amount of any payroll taxes that were deferred by the Company and its subsidiaries under the Coronavirus Aid, Relief, and Economy Security Act (collectively, the “Company Value”). The aggregate transaction consideration to be paid in the Business Combination will consist of the cash consideration to be paid to AdTheorent equityholders, the Class A common stock, par value $0.0001 per share, of MCAP (“MCAP Common Stock”) valued at $10.00 per share that will be delivered to AdTheorent equityholders at the closing of the Business Combination, the restricted stock units in MCAP that will be delivered to holders of AdTheorent interest units, and the options to purchase shares of MCAP Common Stock underlying outstanding vested and unvested stock options. In connection with preserving the aggregate transaction consideration for AdTheorent equityholders in connection with the Business Combination, if options to purchase MCAP Common Stock allocable to holders of vested or unvested stock options become forfeited, such options will be reallocated to the other equityholders of AdTheorent in accordance with the Payment Spreadsheet. In addition, MCAP has agreed to pay an Earn-Out to pre-combination holders of AdTheorent membership interests and options an aggregate amount equal to $95,000,000, to be paid in cash, stock or a combination of both, at the sole discretion of MCAP’s board of directors, if certain stock price milestones are met within three years of the Closing. See the section entitled “Proposal No. 1 — The Business Combination Proposal — The Business Combination Agreement” on page 108 of the accompanying proxy statement/prospectus for further information on the consideration being paid in the Business Combination.

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Based on the capitalization of AdTheorent as of September 30, 2021, the total number of shares of MCAP Common Stock expected to be issued in connection with the Business Combination is approximately 50,234,006, and holders of membership interests in AdTheorent as of immediately prior to the closing of the Business Combination are expected to hold, in the aggregate, approximately 49.6% of the issued and outstanding shares of MCAP Common Stock immediately following the closing of the Business Combination. MCAP’s units, common stock and warrants are currently listed on the Nasdaq Capital Market (“Nasdaq”), under the symbols “MACQU,” “MACQ,” and “MACQW,” respectively. MCAP intends to apply to list the shares of common stock of the post-combination company and such warrants on the Nasdaq Global Market under the symbols “ADTH” and “ADTHW,” respectively, upon the closing of the Business Combination. MCAP will not have units traded following the closing of the Business Combination, at which time each unit will separate into its component securities. Following the closing of the Business Combination, MCAP intends to change its name to AdTheorent Holding Company, Inc.

In connection with the execution of the BCA, MCAP entered into subscription agreements with institutional accredited investors, pursuant to which the investors agreed to purchase an aggregate of 12,150,000 shares of MCAP Common Stock, for a purchase price of $10.00 per share and an aggregate purchase price of $121,500,000. The closing of the sale of these shares pursuant to the subscription agreements is contingent upon, among other customary closing conditions, the substantially concurrent consummation of the Business Combination. See “Certain Agreements Related to the Business Combination — Subscription Agreements.”

MCAP is holding a Stockholders Meeting in lieu of the 2021 annual meeting of its stockholders to obtain the stockholder approvals necessary to complete the Business Combination. At the MCAP Stockholders Meeting, which will be held in a virtual format on December 21, 2021, at 10:00 a.m., Eastern time, unless postponed or adjourned to a later date, MCAP will ask its stockholders to adopt the Business Combination Agreement, thereby approving the Business Combination and approve the other proposals described in the accompanying proxy statement/prospectus.

As described in the accompanying proxy statement/prospectus, certain equityholders of AdTheorent are parties to a stockholder support agreement with MCAP whereby such equityholders, among other things, agreed to vote all of their membership interests in AdTheorent in favor of approving the BCA and the Business Combination. As also described in the accompanying proxy statement/prospectus, the Sponsor (as defined below) is a party to a sponsor support agreement with MCAP and AdTheorent whereby the Sponsor, among other things, agreed to vote all of its shares of MCAP common stock in favor of approving the proposals described in the accompanying proxy statement/prospectus.

After careful consideration, the respective MCAP and AdTheorent boards of directors have unanimously approved the BCA and the Business Combination, and the board of directors of MCAP has approved the other proposals described in the accompanying proxy statement/prospectus, and each of the MCAP and AdTheorent boards of directors has determined that it is advisable to consummate the Business Combination. The board of directors of MCAP recommends that its stockholders vote “FOR” the proposals described in the accompanying proxy statement/prospectus.

More information about MCAP, AdTheorent and the Business Combination is contained in the accompanying proxy statement/prospectus. We urge you to read the accompanying proxy statement/prospectus, including the financial statements and annexes and other documents referred to therein, carefully and in their entirety. IN PARTICULAR, YOU SHOULD CAREFULLY CONSIDER THE MATTERS DISCUSSED UNDER “RISK FACTORS” BEGINNING ON PAGE 43 OF THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS.

On behalf of our board of directors, I thank you for your support and look forward to the successful completion of the Business Combination.

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The accompanying proxy statement/prospectus is dated           , 2021 and is first being mailed to the stockholders of MCAP on or about that date.

NEITHER THE U.S. SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS OR ANY OF THE SECURITIES TO BE ISSUED IN THE BUSINESS COMBINATION, PASSED UPON THE MERITS OR FAIRNESS OF THE BUSINESS COMBINATION OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THE ACCOMPANYING PROXY STATEMENT/PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

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MCAP ACQUISITION CORPORATION

311 South Wacker Drive, Suite 6400

Chicago, Illinois 60606

NOTICE OF STOCKHOLDERS MEETING IN LIEU OF 2021 ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON DECEMBER 21, 2021

To the Stockholders of MCAP Acquisition Corporation:

NOTICE IS HEREBY GIVEN that a special meeting in lieu of the 2021 annual meeting of stockholders (the “Stockholders Meeting”) of MCAP Acquisition Corporation, a Delaware corporation (“MCAP,” “we,” “our” or “us”), which, in light of public health concerns regarding the coronavirus (COVID-19) pandemic, will be held in virtual format on December 21, 2021, at 10:00 a.m., Eastern time. The Stockholders Meeting can be accessed by visiting www.virtualshareholdermeeting.com/MACQ2021SM, where you will be able to listen to the meeting live and vote during the meeting. Please note that you will only be able to access the Stockholders Meeting by means of remote communication.

You are cordially invited to attend the Stockholders Meeting, which will be held for the following purposes:

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The board of directors of MCAP has fixed the close of business on November 4, 2021 as the record date for the determination of the stockholders of MCAP entitled to receive notice of the Stockholders Meeting. Only MCAP stockholders of record at the close of business on the record date for the Stockholders Meeting are entitled to notice of the Stockholders Meeting and any adjournment or postponement of the Stockholders Meeting. Only MCAP stockholders of record at the close of business on the record date for the Stockholders Meeting are entitled to vote at the Stockholders Meeting and any adjournment or postponement of the Stockholders Meeting.

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Your attention is directed to the proxy statement/prospectus accompanying this notice (including the financial statements and annexes attached thereto) for a more complete description of the proposed Business Combination and related transactions and each of our proposals. We encourage you to read the accompanying proxy statement/prospectus carefully. If you have any questions or need assistance voting your shares, please call one of our proxy solicitors, MacKenzie Partners, Inc., at (800) 322-2885 or (212) 929-5500.

All MCAP stockholders are cordially invited to attend the Stockholders Meeting in virtual format. MCAP stockholders may attend, vote and examine the list of MCAP stockholders entitled to vote at the Stockholders Meeting by visiting www.virtualshareholdermeeting.com/MACQ2021SM and using the 16-digit control number included on your proxy card or voting instruction form. In light of public health concerns regarding the COVID-19 pandemic, the Stockholders Meeting will be held in virtual meeting format only. You will not be able to attend the Stockholders Meeting physically. To ensure your representation at the Stockholders Meeting, you are urged to complete, sign, date and return the enclosed proxy card as soon as possible. If your shares are held in an account at a brokerage firm or bank, you must instruct your broker or bank on how to vote your shares.

Your vote is important regardless of the number of shares you own. Whether you plan to attend the Stockholders Meeting or not, please sign, date and return the enclosed proxy card as soon as possible in the envelope provided. If your shares are held in “street name” or are in a margin or similar account, you should contact your broker to ensure that votes related to the shares you beneficially own are properly counted. If you sold or transferred your shares after the record date, it is still important that you vote.

Thank you for your participation. We look forward to your continued support.

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If you return your signed proxy without an indication of how you wish to vote, your shares will be voted in favor of each of the proposals.

All holders (the “Public Stockholders”) of shares of MCAP common stock issued in MCAP’s initial public offering (the “Public Shares”) have the right to have their Public Shares redeemed for cash in connection with the proposed Business Combination. Public Stockholders are not required to affirmatively vote for or against the Business Combination Proposal, to vote on the Business Combination Proposal at all, or to be holders of record on the record date in order to have their shares redeemed for cash. This means that any Public Stockholder holding Public Shares may exercise redemption rights regardless of whether they are even entitled to vote on the Business Combination Proposal.

To exercise redemption rights, holders must tender their stock to Continental Stock Transfer & Trust Company, MCAP’s transfer agent, no later than two business days prior to the Stockholders Meeting. You may tender your stock by either delivering your stock certificate to the transfer agent or by delivering your shares electronically using the Depository Trust Company’s Deposit Withdrawal at Custodian System. If the Business Combination is not completed, then these shares will not be redeemed for cash. If you hold the shares in street name, you will need to instruct your bank or broker to withdraw the shares from your account in order to exercise your redemption rights. See “Stockholders Meeting of MCAP Stockholders — Redemption Rights” for more specific instructions.

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ABOUT THIS PROXY STATEMENT/PROSPECTUS

This document, which forms part of a registration statement on Form S-4 filed with the SEC, by MCAP (File No. 333-259027) (the “Registration Statement”), constitutes a prospectus of MCAP under Section 5 of the Securities Act, with respect to the shares of MCAP Common Stock to be issued if the Business Combination described below is consummated. This document also constitutes a notice of meeting and a proxy statement under Section 14(a) of the Exchange Act with respect to the Stockholders Meeting in lieu of the 2021 annual meeting of MCAP stockholders at which MCAP stockholders will be asked to consider and vote on a proposal to approve the Business Combination by the approval and adoption of the Business Combination Agreement, among other matters.

This proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction.

FREQUENTLY USED TERMS

In this document:

“AdTheorent” means AdTheorent Holding Company, LLC, a Delaware limited liability company.

“AdTheorent Board of Directors” means the board of directors of AdTheorent.

“AdTheorent Membership Interests” means the voting Class A membership interests, non-voting Class B membership interests and non-voting Class C membership interests of AdTheorent.

“AdTheorent Options” means all outstanding options to purchase non-voting Class C membership interests of AdTheorent, as applicable, whether or not exercisable and whether or not vested, immediately prior to the Closing granted under the AdTheorent 2017 Interest Option Plan.

“BCA” or “Business Combination Agreement” means the Business Combination Agreement, dated as of July 27, 2021, as it may be amended and/or restated from time to time, by and among MCAP, AdTheorent, Blocker, Blocker Member and the Merger Subs.

“Blocker” means H.I.G. Growth — AdTheorent Intermediate, LLC, a Delaware limited liability company.

“Blocker Member” means H.I.G. Growth — AdTheorent, LLC, a Delaware limited liability company.

“Business Combination” means the transactions contemplated by the Business Combination Agreement.

“Closing” means the consummation of the Business Combination.

“Closing Date” means the date on which the Closing occurs.

“Company” means, unless context dictates otherwise, AdTheorent prior to the Business Combination, and the Post-Combination Company following the Business Combination.

“Code” means the Internal Revenue Code of 1986, as amended.

“DGCL” means the Delaware General Corporation Law.

“Exchange Act” means the U.S. Securities Exchange Act of 1934, as amended.

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“Exchanged Options” means the options to purchase shares of MCAP Common Stock issued at the Effective Time, pursuant to and subject to the terms set forth in the BCA and by virtue of the Mergers, upon conversion of AdTheorent Options that are outstanding immediately prior to the Effective Time.

“Exchanged Units” means the restricted stock units with respect to shares of MCAP Common Stock issued at the Effective Time, pursuant to and subject to the terms set forth in the BCA and by virtue of the Mergers, upon conversion of restricted interest units with respect to a Class C membership interest of AdTheorent that are outstanding immediately prior to the Effective Time.

“Founder Shares” means the shares of MCAP Class B common stock initially purchased by the Sponsor in a private placement in December 2020 and those issued to the Sponsor pursuant to a stock dividend on February 25, 2021.

“GAAP” means United States generally accepted accounting principles.

“Investment Company Act” means the Investment Company Act of 1940, as amended.

“IPO” means MCAP’s initial public offering of units, consummated on February 25, 2021.

“JOBS Act” means the Jumpstart Our Business Startups Act of 2012, as amended.

“Key Company Members” means Blocker, Blocker Member, Monroe Capital Corporation, Monroe Capital Private Credit Fund II LP, Monroe Capital Private Credit Fund II (Unleveraged) LP, Monroe Private Credit Fund A LP, Monroe Capital Private Credit Fund I LP and Monroe Capital Partners Fund LP.

“Lock-Up Agreement” means the Lock-Up Agreement to be entered into in connection with the Closing by MCAP, certain MCAP stockholders (including the Sponsor) and certain AdTheorent members in the form attached to this proxy statement/prospectus as Annex I.

“MCAP” means MCAP Acquisition Corporation, a Delaware corporation.

“MCAP Board” means the board of directors of MCAP.

“MCAP Common Stock” means MCAP’s Class A common stock, par value $0.0001 per share.

“MCAP Unit” means one share of MCAP Common Stock and one MCAP Warrant sold in the IPO.

“MCAP Warrant Agreement” means the warrant agreement, dated as of February 25, 2021, by and between MCAP and Continental Stock Transfer & Trust Company, governing MCAP’s outstanding warrants.

“MCAP Warrants” means warrants to purchase shares of MCAP Common Stock as contemplated under the MCAP Warrant Agreement, with each whole warrant exercisable for one share of MCAP Common Stock at an exercise price of $11.50 per whole share.

“Member Support Agreement” means the Member Support Agreement, dated as of July 27, 2021, by and among MCAP, AdTheorent and the Key Company Members in the form attached to this proxy statement/prospectus as Annex F.

“Mergers” means, collectively, the First Company Merger, the Second Company Merger and the Blocker Mergers as defined in and contemplated by the BCA.

“Merger Sub 1” means GRNT Merger Sub 1, LLC, a Delaware limited liability company and wholly owned subsidiary of MCAP.

“Merger Sub 2” means GRNT Merger Sub 2, LLC, a Delaware limited liability company and wholly owned subsidiary of MCAP.

“Merger Sub 3” means GRNT Merger Sub 3, LLC, a Delaware limited liability company and wholly owned subsidiary of MCAP.

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“Merger Sub 4” means GRNT Merger Sub 4, LLC, a Delaware limited liability company and wholly owned subsidiary of MCAP.

“Merger Subs” means, collectively, Merger Sub 1, Merger Sub 2, Merger Sub 3 and Merger Sub 4.

“Nasdaq” means the Nasdaq Capital Markets.

“PCAOB” means the Public Company Accounting Oversight Board.

“PCAOB Audited Financials” means (a) the audited consolidated balance sheet of AdTheorent as of December 31, 2019 and December 31, 2020, and the related audited consolidated statements of income and cash flows of AdTheorent for the years ended December 31, 2019, and December 31, 2020, each audited in accordance with the auditing standards of the PCAOB and Generally Accepted Auditing Standards and included in this proxy statement/prospectus and (b) the reviewed consolidated balance sheet of AdTheorent as of September 30, 2020, and the related unaudited consolidated statements of income and cash flows of AdTheorent for the nine month period ended September 30, 2021, each audited in accordance with the auditing standards of the PCAOB and Generally Accepted Auditing Standards and included in this proxy statement/prospectus.

“PIPE Financing” means the sale of PIPE Shares to the Subscribers, for a purchase price of $10.00 per share for an aggregate purchase price of $121.5 million, in a private placement.

“PIPE Shares” means an aggregate of 12,150,000 shares of MCAP Common Stock to be issued to Subscribers in the PIPE Financing, for a purchase price of $10.00 per share.

“Post-Combination Company” means MCAP immediately upon the consummation of the Business Combination.

“Private Placement Warrants” means the warrants to purchase shares of MCAP Common Stock purchased in a private placement in connection with the IPO.

"Proposed Charter" means the Second Amended and Restated Certificate of Incorporation, in the form attached to this proxy statement/prospectus as Annex B, which, if approved, would take effect upon the Closing.

“prospectus” means the prospectus included in the Registration Statement on Form S-4 (Registration No. 333-259027) filed with the SEC.

“Public Shares” means shares of MCAP Common Stock issued as part of the units sold in the IPO.

“Public Stockholders” means the holders of Public Shares.

“Public Warrants” means the warrants included in the units sold in the IPO, each of which is exercisable for one share of MCAP Common Stock, in accordance with its terms.

“Registration Rights Agreement” means the Amended and Restated Registration Rights Agreement of MCAP to be entered into in connection with the Closing by MCAP, certain AdTheorent members and certain MCAP stockholders (including the Sponsor) in the form attached to this proxy statement/prospectus as Annex H.

“SEC” means the U.S. Securities and Exchange Commission.

“Securities Act” means the U.S. Securities Act of 1933, as amended.

“Stockholders Meeting” means the Stockholders Meeting in lieu of the 2021 annual meeting of the stockholders of MCAP that is the subject of this proxy statement/prospectus.

“Sponsor” means MCAP Acquisition, LLC, a Delaware limited liability company.

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“Sponsor Support Agreement” means the Sponsor Support Agreement, dated as of July 27, 2021, by and among Sponsor, AdTheorent and MCAP in the form attached to this proxy statement/prospectus as Annex G.

“Stockholders Agreement” means the Stockholders Agreement to be entered into in connection with the Closing by MCAP, the Sponsor and certain AdTheorent members in the form attached to this proxy statement/prospectus as Annex J.

“Trust Account” means the trust account that holds a portion of the proceeds of the IPO and the concurrent sale of the Placement Units.

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SUMMARY OF THE PROXY STATEMENT/PROSPECTUS

This summary highlights selected information from this proxy statement/prospectus and does not contain all of the information that might be important to you. To better understand the Business Combination and the proposals to be considered at the Stockholders Meeting, you should read this proxy statement/prospectus carefully and in its entirety, including the annexes. See also the section entitled “Where You Can Find More Information.”

Parties to the Business Combination

MCAP

MCAP Acquisition Corporation (“MCAP”) is a blank check company incorporated in Delaware on November 12, 2020. MCAP was formed for the purpose of effectuating a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or other similar business combination with one or more businesses. On December 21, 2020, MCAP issued an aggregate of 7,187,500 shares of Class B common stock (the “Founder Shares”) to MCAP Acquisition, LLC (the “Sponsor”) for an aggregate purchase price of $25,000, or approximately $0.003 per share. On February 25, 2021, MCAP effected a 0.1 for 1 dividend of its Class B common stock, resulting in an aggregate 7,906,250 Founder Shares issued and outstanding. Such shares had an aggregate market value of approximately $78.6 million, based on the last sale price of MCAP Common Stock of $9.94 per share on Nasdaq on December 1, 2021.

On March 2, 2021, MCAP consummated its IPO of 31,625,000 units. Each unit consists of one share of Class A common stock and one-third of one redeemable warrant, with each whole warrant entitling the holder thereof to purchase one share of Class A common stock for $11.50 per share. The units were sold at a price of $10.00 per unit, generating gross proceeds of $316,250,000. Simultaneously with the closing of its IPO, MCAP consummated the sale of 5,983,333 private placement warrants (the “Private Placement Warrants”) at a price of $1.50 per warrant in a private placement to the Sponsor, generating gross proceeds of $8,975,000. Such warrants had an aggregate market value of approximately $6.9 million based on the last sale price of $1.16 per warrant on Nasdaq on December 1, 2021.

Following the closing of MCAP’s IPO on March 2, 2021, an amount of $316,250,000 ($10.00 per unit) from the net proceeds of the sale of the units in the IPO and the Private Placement Warrants was placed in a trust account established for the benefit of the Public Stockholders (the “Trust Account”) and the remaining proceeds became available to be used to provide for business, legal and accounting due diligence on prospective business combinations and continuing general and administrative expenses. As of September 30, 2021, MCAP had approximately $316.3 million held in the Trust Account.

MCAP’s principal executive offices are located at 311 South Wacker Drive, Suite 6400, Chicago, Illinois 60606 and its phone number is (312) 258-8300.

Merger Subs

GRNT Merger Sub 1 LLC (“Merger Sub 1”), GRNT Merger Sub 2 LLC (“Merger Sub 2”), GRNT Merger Sub 3 LLC (“Merger Sub 3”) and GRNT Merger Sub 4 LLC (“Merger Sub 4”) are each Delaware limited liability companies and wholly-owned subsidiaries of MCAP. In the Mergers, Merger Sub 1 will merge with and into H.I.G. Growth — AdTheorent Intermediate, LLC, with H.I.G. Growth — AdTheorent Intermediate, LLC surviving as a wholly-owned subsidiary of MCAP, immediately thereafter, the merger of H.I.G. Growth — AdTheorent Intermediate, LLC with and into Merger Sub 2, with Merger Sub 2 surviving as a wholly-owned subsidiary of MCAP, immediately thereafter, the merger of Merger Sub 3 with and into AdTheorent, with AdTheorent surviving as a wholly-owned subsidiary of MCAP and immediately thereafter, the merger of AdTheorent with and into Merger Sub 4, with Merger Sub 4 surviving as a wholly owned subsidiary of MCAP. Prior to the Business Combination, no Merger Sub has had any business activity or operations other than in preparation for the Business Combination.

Each Merger Sub’s principal executive offices are located at 311 South Wacker Drive, Suite 6400, Chicago, Illinois 60606 and its phone number is (312) 258-8300.

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AdTheorent

AdTheorent Holding Company, LLC is a digital media platform which focuses on performance-first, privacy-forward methods to execute programmatic digital advertising campaigns, serving both advertising agency and brand customers. AdTheorent, Inc. was incorporated under the laws of the state of Delaware on October 7, 2011. AdTheorent Holding Company, LLC was formed under the laws of the State of Delaware on December 9, 2016. The mailing address of AdTheorent’s principal executive office is 330 Hudson Street, 13th Floor, New York, NY 10013, and its telephone number is (800) 804-1359.

Emerging Growth Company

MCAP is an “emerging growth company,” as defined under the JOBS Act. As an emerging growth company, MCAP is eligible to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. These include, but are not limited to, not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002, reduced disclosure obligations regarding executive compensation in its periodic reports and proxy statements, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and the requirement to obtain stockholder approval of any golden parachute payments not previously approved.

Following the Business Combination, AdTheorent will remain an emerging growth company until the earlier of (i) the last day of the fiscal year in which the market value of its common stock that are held by non-affiliates is equal to or exceeds $700 million as of the end of that year’s second fiscal quarter, (ii) the last day of the fiscal year in which it has total annual gross revenue of $1.07 billion or more during such fiscal year (as indexed for inflation), (iii) the date on which it has issued more than $1 billion in non-convertible debt in the prior three-year period or (iv) the last day of the fiscal year following the fifth anniversary of the date of the first sale of MCAP Common Stock in the IPO.

The Proposals to be Submitted at the Stockholders Meeting

Proposal No. 1: The Business Combination Proposal

MCAP and AdTheorent have agreed to the Business Combination under the terms of the BCA. Pursuant to the terms of the BCA, and subject to the satisfaction or waiver of the conditions to the Closing therein, at the Closing, Merger Sub 1 will merge with and into H.I.G. Growth — AdTheorent Intermediate, LLC, with H.I.G. Growth — AdTheorent Intermediate, LLC surviving as a wholly-owned subsidiary of MCAP, immediately thereafter, the merger of H.I.G. Growth — AdTheorent Intermediate, LLC with and into Merger Sub 2, with Merger Sub 2 surviving as a wholly-owned subsidiary of MCAP, immediately thereafter, the merger of Merger Sub 3 with and into AdTheorent, with AdTheorent surviving as a wholly-owned subsidiary of MCAP and immediately thereafter, the merger of AdTheorent with and into Merger Sub 4, with Merger Sub surviving as a wholly-owned subsidiary of MCAP. Unless waived by the applicable party or parties to the BCA, and subject to applicable law, the completion of the Business Combination is subject to a number of conditions set forth in the BCA, including, among others, that (a) the amount available for the Aggregate Cash Consideration shall be equal to at least one hundred forty million dollars ($140,000,000) (subject to MCAP’s option to attempt to make up Aggregate Cash Consideration shortfalls in a number of methods described herein) and (b) the Available Cash shall be equal to at least two hundred fifty eight million one hundred twenty five thousand dollars ($258,125,000). Please see the sections entitled “Proposal No. 1  —  The Business Combination Proposal” and “The Business Combination Agreement” for more information about the Business Combination and the Business Combination Agreement.

Other Agreements Relating to the Business Combination

Registration Rights Agreement

Contemporaneously with the Closing, MCAP, certain MCAP Stockholders (including the Sponsor) and certain AdTheorent members (including the Key Company Members) (such stockholders, the “Holders”) will enter into a Registration Rights Agreement in the form attached to this proxy statement/prospectus as Annex H, pursuant to which, among other things, MCAP will be obligated to file a registration statement to register the resale of certain securities of MCAP held by the Holders. The Registration Rights Agreement will also provide the Holders with “piggy-back” registration rights, subject to certain requirements and customary conditions. For more information on the Registration Rights Agreement, please see the section entitled “Proposal No. 1  —  The Business Combination Proposal — Related Agreements — Registration Rights Agreement.”

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Lock-Up Agreement

Contemporaneously with the Closing, MCAP and the Holders will enter into a Lock-up Agreement in the form attached to this proxy statement/prospectus as Annex I, which, among other things, and subject to certain exceptions, provides for the MCAP Common Stock held by the Holders to be locked-up for a period of six (6) months from the Closing Date in accordance with the terms set forth therein. For more information on the Lock-up Agreement, please see the section entitled “Proposal No. 1  —  The Business Combination Proposal — Related Agreements — Lock-up Agreement.”

Stockholders Agreement

Contemporaneously with the Closing, MCAP, the Sponsor and certain AdTheorent members (including the Key Company Members) will enter into the Stockholders Agreement in the form attached to this proxy statement/prospectus as Annex J, which will provide, among other things, that the post-Closing board of directors of MCAP will consist of nine (9) directors. Additionally, the Stockholders Agreement will provide that three (3) directors are to be independent directors, four (4) directors are to be nominated by H.I.G. (the “H.I.G. Designees”) for so long as H.I.G. Beneficially Owns 20% or more of the outstanding shares of Common Stock of AdTheorent, three (3) directors are to be nominated by H.I.G. for so long as H.I.G. Beneficially Owns 15% or more (but less than 20%) of the outstanding shares of Common Stock of AdTheorent, two (2) directors are to be nominated by H.I.G. for so long as H.I.G. Beneficially Owns 10% or more (but less than 15%) of the outstanding shares of Common Stock of AdTheorent, and one (1) director nominated by H.I.G. for so long as H.I.G. Beneficially Owns 5% or more (but less than 10%) of the outstanding shares of Common Stock of AdTheorent. In addition, the Stockholders Agreement will provide for one (1) director to be nominated by Sponsor (the “Sponsor Designee” and together with the H.I.G. Designees, the “Designees”) for so long as Sponsor and its Affiliates Beneficially Own 1% or more of the outstanding shares of Common Stock of AdTheorent. For more information on the Stockholders Agreement, please see the section entitled “Proposal No. 1  —  The Business Combination Proposal — Related Agreements — Stockholders Agreement.”

Member Support Agreement

In connection with the execution of the BCA, AdTheorent and the Key Company Members entered into the Member Support Agreement pursuant to which, among other things, the Key Company Members agreed to:

For more information on the Member Support Agreement, please see the section entitled “Certain Agreements Related to the Business Combination — Member Support Agreement.”

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Sponsor Support Agreement

In connection with the execution of the BCA, MCAP, AdTheorent, and the Sponsor entered into the Sponsor Support Agreement pursuant to which, among other things, the Sponsor agreed to:

For more information on the Sponsor Support Agreement, please see the section entitled “Certain Agreements Related to the Business Combination — Sponsor Support Agreement.”

Subscription Agreements

MCAP obtained commitments from certain investors (each, a “PIPE Investor”) to purchase shares of MCAP Common Stock (such shares, collectively, “PIPE Shares”) in an aggregate value of $121,500,000 (as of the date hereof), representing 12,150,000 Subscription Shares at a price of $10.00 per share. The purpose of the sale of the PIPE Shares is to raise additional capital for use in connection with the Transactions and to meet the minimum cash requirements provided in the BCA. The closing of the sale of the PIPE Shares pursuant to the Subscription Agreement is contingent upon, among other customary closing conditions, the substantially concurrent consummation of the Business Combination. Members of our Sponsor or their affiliates have committed to purchase an aggregate of 2,650,000 PIPE Shares. For more information on the Subscription Agreements in the form attached to this proxy statement/prospectus as Annex K, please see the section entitled “Proposal No. 1  —  The Business Combination Proposal — Related Agreements — Subscription Agreements.”

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Organizational Structure

Prior to the Business Combination

The diagrams below depict simplified versions of the current organizational structures of MCAP and AdTheorent, respectively, prior to the Business Combination.

MCAP

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AdTheorent/Symetry Companies

(As of April 28, 2021)

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After the Business Combination

The diagram below depicts a simplified version of our organizational structure immediately following the completion of the Business Combination.

The ownership of the Post-Combination Company immediately following the Business Combination will be as follows:

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The “Illustrative Maximum Redemption Scenario” assumes that MCAP Public Stockholders exercise redemption rights with respect to 44% of the outstanding shares of Class A Common Stock. This scenario assumes that 13,769,947 shares of Class A Common Stock are redeemed for an aggregate payment of approximately $137.7 million from the Trust Account, which is the maximum amount of redemptions, without a shortfall of cash, while still satisfying the “Aggregate Cash Consideration” condition to the consummation of the Business Combination. Although not reflected in the illustrative maximum redemption scenario, if redemptions exceed 44%, to the extent there is a shortfall of available cash to pay at least $140.0 million of Aggregate Cash Consideration to AdTheorent’s members and thus satisfy the Aggregate Cash Consideration closing condition, which can only be waived by AdTheorent members in their sole discretion, MCAP has the option under the BCA, in its sole discretion, to make up such shortfall by (i) raising additional funds in a private investment in public equity (“PIPE”) and applying such funds to such shortfall, (ii) causing a portion of AdTheorent’s indebtedness to remain outstanding and applying any funds which would otherwise have been applied towards paying off such indebtedness to such shortfall, (iii) requiring AdTheorent or an AdTheorent subsidiary to incur additional indebtedness in an amount not to exceed such shortfall upon commercially reasonable terms mutually agreed upon by MCAP and AdTheorent, each acting in good faith, and applying any such funds to such shortfall, and/or (iv) using a portion of the Balance Sheet Funding Amount and applying any such funds to such shortfall. The shortfall can be resolved using solely one option or a combination of the aforementioned options. If redemptions are 57% or higher, there would be insufficient cash in trust to satisfy the Available Cash closing condition, which can only be waived by AdTheorent members in their sole discretion. In the event redemptions are higher than 57% and AdTheorent members elect to waive the Available Cash closing condition, the transaction could still be consummated if the parties are able to arrange for financing through one or a combination of the levers described above to make up for the shortfall of available cash to pay at least $140.0 million in Aggregate Cash Consideration to AdTheorent’s members, or if AdTheorent members agree to waive or lower the Aggregate Cash Consideration closing condition. Since these scenarios would require the waiver of the AdTheorent members, have not been negotiated and would require the parties to identify sources of financing that either may not be available or may not be available on terms that are acceptable, these scenarios have not been considered in the Illustrative Maximum Redemptions scenario. However, if redemptions exceed 57% and the transaction is still consummated, the resulting impact could be materially different from what is being disclosed in the Illustrative Maximum Redemptions scenario. See Note 2 to “Notes to Unaudited Pro Forma Condensed Combined Financial Information” for further description of the Illustrative Maximum Redemption scenario and a sensitivity analysis showing the impact if redemptions exceed the level shown in this scenario and the transaction is still consummated. There can be no assurance regarding which scenario will be closest to the actual results.

In addition, upon consummation of the Business Combination, and giving effect to the Sponsor’s forfeiture of 551,096 Private Placement Warrants, there will be outstanding an aggregate of 10,541,667 Public Warrants and 5,432,237 Private Placement Warrants held by our Sponsor (551,096 of which will be subject to escrow and forfeiture unless certain earn-out targets are achieved as set forth in the BCA). Each of our outstanding whole warrants is exercisable commencing 30 days following the Closing, for one share of MCAP Common Stock. Therefore, as of the date of this proxy statement/prospectus, if we assume that each outstanding whole warrant is exercised and one share of MCAP Common Stock is issued as a result of such exercise, with payment to MCAP of the exercise price of $11.50 per whole warrant for one whole share, our fully-diluted share capital would increase by a total of 15,973,904 shares, with approximately $183.7 million paid to us to exercise the warrants, assuming cash exercise.

The numbers of shares and percentage interests set forth in the above table under either redemption scenario do not take into account (i) potential future exercises of up to 10,541,667 Public Warrants and up to 5,432,237 Private Placement Warrants (551,096 of which are to be held in escrow subject to earn-out targets), which will remain outstanding immediately following the Business Combination and may be exercised thereafter at an exercise price of $11.50 (commencing 30 days after the Closing of the Business

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Combination), (ii) 598,875 Founder Shares owned by the Sponsor but held in escrow subject to the achievement of earn-out targets as described in the BCA, (iii) 8,375,241 shares issuable upon the exercise of outstanding options to purchase shares of AdTheorent membership interests, (iv) up to 10,131,638 shares issuable pursuant to the AdTheorent 2021 Long-Term Incentive Plan, (v) up to 2,026,328 shares issuable pursuant to the AdTheorent 2021 Employee Stock Purchase Plan or (vi) warrants to purchase up to 1,000,000 shares if the Sponsor makes a working capital loan prior to the closing of the Business Combination in an amount up to $1,500,000 (no such loans have been made to date). The exercise, issuance or vesting of any of these shares could have a dilutive effect on those of our stockholders who do not elect to redeem their shares. If all such shares were issued immediately after the Business Combination, based on the number of issued and outstanding shares of MCAP Common Stock and AdTheorent Capital Stock on September 30, 2021, and based on the MCAP Common Stock expected to be issued in the Business Combination and the PIPE Financing, non-redeeming Public Stockholders, as a group, would own:

If the actual facts are different than the assumptions set forth above, the share numbers set forth above will be different. For more information, please see the section entitled "Unaudited Pro Forma Condensed Combined Financial Information.”

Proposal No. 2 — The Charter Amendment Proposal

MCAP is proposing that its stockholders vote to approve and adopt an amendment to MCAP’s current certificate of incorporation. A summary of the Charter Amendment Proposal is set forth in the section entitled “Proposal No. 2 — The Charter Amendment Proposal” of this proxy statement/prospectus.

Proposal No. 3 — The Advisory Charter Proposals

MCAP is proposing that its stockholders consider and vote upon, on a non-binding advisory basis, a proposal to approve certain governance provisions contained in the Proposed Charter, being presented in accordance with the requirements of the U.S. Securities and Exchange Commission (the “SEC”) as eight separate sub-proposals (which we refer to, collectively, as the “Advisory Charter Proposals”):

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Proposal No. 4 — The Election of Directors Proposal

MCAP is proposing that its stockholders vote to elect nine directors to serve staggered terms on the MCAP Board until the 2022, 2023 and 2024 annual meeting of stockholders of MCAP, respectively, and until their respective successors are duly elected and qualified. A summary of the Director Election Proposal is set forth in the section entitled “Proposal No. 4 — The Director Election Proposal” of this proxy statement/prospectus.

Proposal No. 5 — The Long-Term Incentive Plan Proposal

MCAP is proposing that its stockholders vote to approve the 2021 Long-Term Incentive Plan to be effective after the closing of the Business Combination. We refer to this proposal as the “Equity Incentive Plan Proposal.” A copy of the 2021 Long-Term Incentive Plan is attached hereto as Annex D.

Proposal No. 6 — The ESPP Proposal

MCAP is proposing that its stockholders vote to approve the 2021 Employee Stock Purchase Plan (“ESPP”) to be effective after the closing of the Business Combination. We refer to this proposal as the “ESPP Proposal.” A copy of the 2021 Employee Stock Purchase Plan is attached hereto as Annex E.

Proposal No. 7 — The Nasdaq Proposal

MCAP is proposing that its stockholders vote to approve (i) for purposes of complying with Nasdaq Listing Rules 5635(a) and (b), the issuance of more than 20% of the issued and outstanding Class A common stock and the resulting change in control in connection with the Business Combination, and (ii) for the purpose of complying with Nasdaq Listing Rule 5635(d), the issuance of more than 20% of the issued and outstanding shares of Class A common stock in the PIPE Financing upon the completion of the Business Combination. A summary of the Nasdaq Proposal is set forth in the section entitled “Proposal No. 7 —  The Nasdaq Proposal” of this proxy statement/prospectus.

Proposal No. 8 — The Stockholder Adjournment Proposal

The Stockholder Adjournment Proposal, if adopted, will allow the MCAP Board to adjourn the Stockholders Meeting to a later date or dates, including, if necessary to permit further solicitation and vote of proxies if it is determined by MCAP that more time is necessary or appropriate to approve one or more Stockholder Proposals at the Stockholders Meeting. A summary of the Shareholder Adjournment Proposal is set forth in the section entitled “Proposal No. 8  —  The Shareholder Adjournment Proposal” of this proxy statement/prospectus.

The Stockholders Meeting

Date, Time and Place of Stockholders Meeting

The Stockholders Meeting will be held at 10:00 a.m. Eastern Time, on December 21, 2021, or at such other date, time and place to which such meeting may be adjourned and also via live webcast at www.virtualshareholdermeeting.com/MACQ2021SM to consider and vote upon the Stockholder Proposals, as a virtual meeting.

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Record Date; Outstanding Shares; Stockholders Entitled to Vote

MCAP has fixed the close of business on November 4, 2021, as the Record Date for determining the MCAP stockholders entitled to notice of and to attend and vote at the Stockholders Meeting.

As of the close of business on such date, there were 31,625,000 shares of Class A common stock and 7,906,250 Founder Shares outstanding and entitled to vote. The shares of Class A common stock and the Founder Shares vote together as a single class, except in the election of directors, as to which only the Founder Shares vote, and each share is entitled to one vote per share at the Stockholders Meeting. The Sponsor owns 7,906,250 Founder Shares, which are shares of Class B common stock of MCAP. Pursuant to the Insider Letter Agreement among MCAP, the Sponsor and MCAP’s directors and officers, (i) the 7,906,250 Founder Shares owned by the Sponsor and (ii) any other shares of common stock of MCAP owned by the Sponsor or MCAP’s officers and directors will be voted in favor of the Business Combination at the Stockholders Meeting.

Proxy Solicitation

Proxies with respect to the Stockholders Meeting may be solicited by telephone, by facsimile, by mail, on the internet or in person. MCAP has engaged Broadridge Financial Solutions, Inc. and MacKenzie Partners, Inc. to assist in the solicitation of proxies. If a stockholder grants a proxy, it may still vote its shares at the virtual meeting if it revokes its proxy before the Stockholders Meeting. A stockholder may also change its vote by submitting a later-dated proxy, as described in the section entitled “Stockholders Meeting — Revoking Your Proxy — Changing Your Vote.”

Quorum and Required Vote

A quorum of MCAP stockholders is necessary to hold the Stockholders Meeting. The presence, in person or by proxy, of MCAP stockholders representing a majority of the shares of common stock issued and outstanding on the Record Date and entitled to vote on the Stockholder Proposals to be considered at the Stockholders Meeting will constitute a quorum for the Stockholders Meeting.

Each of the Business Combination Proposal, Charter Amendment Proposal, Election of Directors Proposal, Long-Term Incentive Plan Proposal, Employee Stock Purchase Plan Proposal and Nasdaq Proposal is interdependent upon the others and must be approved in order for MCAP to complete the Business Combination as contemplated by the BCA. Other than the Director Election Proposal, each of the Stockholder Proposals require the affirmative vote of a majority of the issued and outstanding shares of MCAP common stock cast by the stockholders represented in person (which would include presence at a virtual meeting) or by proxy at the Stockholders Meeting and entitled to vote thereon, voting as a single class. Under MCAP’s charter, the election of directors under the Director Election Proposal requires a plurality vote of the Founder Shares present in person (which would include presence at a virtual meeting) or represented by proxy and entitled to vote at the Stockholders Meeting. This means that a director nominee will be elected if such director receives more affirmative votes than any other nominee for the same position.

Regulatory Approvals

The Business Combination and the transactions contemplated by the BCA are not subject to any regulatory requirement or approval, except for (i) filings with the State of Delaware to effect the Mergers, (ii) filings required with the SEC pursuant to the reporting requirements applicable to MCAP, and the requirements of the Securities Act and the Exchange Act, including the requirement to file the registration statement of which this proxy statement/prospectus forms a part and to disseminate this proxy statement/prospectus to MCAP’s stockholders and (iii) filings required under the HSR Act in connection with the Business Combination. MCAP must comply with applicable United States federal and state securities laws in connection with the PIPE Financing, and with Nasdaq continued listing requirements, including the filing with Nasdaq of a press release disclosing the Business Combination, among other things.

Appraisal Rights

MCAP’s stockholders do not have appraisal rights under the DGCL or otherwise in connection with the Business Combination Proposal or the other Stockholder Proposals.

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Redemption Rights

Pursuant to MCAP’s charter, a Public Stockholder may request that MCAP redeem all or a portion of such Public Stockholder’s Public Shares for cash if the Business Combination is consummated. You will be entitled to receive cash for any Public Shares to be redeemed only if you:

As noted above, holders of units must elect to separate the underlying Public Shares and Public Warrants prior to exercising redemption rights with respect to the Public Shares. If holders hold their units in an account at a brokerage firm or bank, holders must notify their broker or bank that they elect to separate the units into the underlying Public Shares and Public Warrants, or if a holder holds units registered in its own name, the holder must contact the Transfer Agent directly and instruct it to do so.

Public Stockholders may elect to redeem all or a portion of their Public Shares regardless whether they vote for or against the Business Combination Proposal. If the Business Combination is not consummated, the Public Shares will not be redeemed for cash. If a Public Stockholder properly exercises its right to redeem its Public Shares and timely delivers its share certificates (if any) and other redemption forms to the Transfer Agent, MCAP will redeem each such Public Share for a per share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account calculated as of two business days prior to the consummation of the Business Combination, including interest earned on the funds held in the Trust Account (net of taxes payable), divided by the number of then-outstanding Public Shares. As of September 30, 2021, this would have amounted to approximately $10.0006 per Public Share.

If a Public Stockholder exercises its redemption rights, then it will be exchanging its redeemed Public Shares for cash and will no longer own such shares. Any request to redeem Public Shares, once made, may not be withdrawn once submitted to MCAP unless the MCAP Board determines (in its sole discretion) to permit the withdrawal of such redemption request (which it may do in whole or in part). The holder can make such request by contacting the Transfer Agent, at the address or email address listed in this proxy statement/prospectus. MCAP will be required to honor such request only if made prior to the deadline for exercising redemption requests. See “Stockholders Meeting — Redemption Rights” for a detailed description of the procedures to be followed if you wish to redeem your Public Shares for cash.

Notwithstanding the foregoing, a holder of Public Shares, together with any affiliate of such Public Stockholder or any other person with whom such Public Stockholder is acting in concert or as a “group” (as defined in Section 13 of the Exchange Act), will be restricted from redeeming its Public Shares with respect to more than an aggregate of 15% of the Public Shares. Accordingly, if a Public Stockholder, alone or acting in concert or as a group, seeks to redeem more than 15% of the Public Shares, then any such shares in excess of that 15% limit would not be redeemed for cash.

In order for Public Stockholders to exercise their redemption rights in respect of the Business Combination Proposal, Public Stockholders must properly exercise their right to redeem the Public Shares they hold no later than the close of the vote on the Business Combination Proposal and deliver their share certificates (if any) and other redemption forms (either physically or electronically) to the transfer agent prior to 5:00 p.m., Eastern Time, on December 17, 2021 (two business days prior to the vote at the Stockholders Meeting). Immediately following the consummation of the Business Combination, MCAP will satisfy the exercise of redemption rights by redeeming the Public Shares issued to the Public Stockholders that validly exercised their redemption rights.

Holders of MCAP’s Private Placement Warrants will not have redemption rights with respect to any of those securities (including any shares underlying such Private Placement Warrants).

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Material U.S. Federal Income Tax Consequences

The Company Mergers are intended to qualify as a “reorganization” within the meaning of Section 368(a) of the Code. The parties to the Business Combination have agreed to report the Company Mergers in accordance with such qualification for all tax purposes (unless otherwise required by a judicial or administrative determination). Such qualification, however, involves uncertainty because it assumes facts and representations that cannot be confirmed until after the Closing, including the number of AdTheorent equityholders, if any, who exercise appraisal rights in connection with the Company Mergers. The Company Mergers will occur even if it does not qualify as a reorganization.

For a description of the material U.S. federal income tax consequences of the Business Combination, please see the information set forth in the section entitled “Material U.S. Federal Income Tax Considerations.”

Anticipated Accounting Treatment of the Business Combination

The Business Combination will be accounted for as a reverse recapitalization, in accordance with GAAP. Under this method of accounting, although MCAP will issue shares for outstanding equity interests of AdTheorent in the Business Combination, MCAP will be treated as the “acquired” company for financial reporting purposes. Accordingly, the Business Combination will be treated as the equivalent of AdTheorent issuing stock for the net assets of MCAP, accompanied by a recapitalization. The net assets of MCAP will be stated at carrying value, with no goodwill or other intangible assets recorded. Operations prior to the Business Combination will be those of AdTheorent.

Interests of Certain Persons in the Business Combination

When you consider the recommendation of the MCAP Board in favor of adoption of the Business Combination Proposal, you should keep in mind that MCAP’s directors and officers have interests in the Business Combination that are different from, or in addition to, your interests as a stockholder. The existence of any financial and personal interests of one or more of MCAP’s directors may be argued to result in a conflict of interest on the part of such director(s) between what he, she or they may believe is in the best interests of MCAP and its stockholders and what he, she or they may believe is best for himself, herself or themselves in determining to recommend that stockholders vote for the Stockholder Proposals. See the section entitled “Proposal No. 1 — The Business Combination Proposal — Interests of MCAP’s Directors and Officers and Others in the Business Combination” in this proxy statement/prospectus for a further discussion of such interests and potential conflicts of interest.

Risk Factors

In evaluating the Stockholder Proposals set forth in this proxy statement/prospectus, you should carefully read this proxy statement/prospectus, including the annexes, and especially consider the factors discussed in the section entitled “Risk Factors” beginning on page 43.

Risk Factors Summary

The transactions described in this proxy statement/prospectus involve various risks, and you should carefully read and consider the factors discussed under “Risk Factors.” The following is a summary of some of these risks:

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Recommendation to Stockholders of MCAP

The MCAP Board unanimously recommends that stockholders:

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​

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QUESTIONS AND ANSWERS ABOUT THE BUSINESS COMBINATION

The following questions and answers briefly address some commonly asked questions about the proposals to be presented at the Stockholders Meeting of MCAP stockholders, including with respect to the proposed Business Combination. The following questions and answers may not include all the information that is important to MCAP stockholders. Stockholders are urged to read carefully this entire proxy statement/prospectus, including the financial statements and annexes attached hereto and the other documents referred to herein.

MCAP’s stockholders are being asked to consider and vote upon the Stockholder Proposals described below. Holders of shares of Class B common stock are also being asked to vote upon the Director Election Proposal.

The presence, in person or by proxy, of MCAP stockholders representing a majority of the issued and outstanding common stock on the Record Date and entitled to vote on the Stockholder Proposals to be considered at the Stockholders Meeting, including a majority of the issued and outstanding shares of Class B common stock as of the Record Date in the case of the Director Election Proposal, will constitute a quorum for the Stockholders Meeting.

YOUR VOTE IS IMPORTANT. YOU ARE ENCOURAGED TO VOTE AS SOON AS POSSIBLE AFTER CAREFULLY REVIEWING THIS PROXY STATEMENT/PROSPECTUS.

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Under MCAP’s amended and restated certificate of incorporation, MCAP must provide all Public Stockholders with the opportunity to have their Public Shares redeemed for cash upon the consummation of MCAP’s initial business combination in conjunction with a stockholder vote.

Each option to purchase a Class C membership interest of AdTheorent outstanding immediately prior to the effective time of the Business Combination, whether vested or unvested, will be converted into (i) options to purchase New MCAP Stock and (ii) a portion of the Earn-Out Consideration. Each restricted interest unit with respect to a Class C membership interest of AdTheorent outstanding immediately prior to the effective time of the Business Combination, whether vested or unvested, will be converted into (i) restricted stock units with respect to New MCAP Stock and (ii) a portion of the Earn-Out Consideration. Consistent with the terms of the BCA, the total number of shares of MCAP Common Stock issued to holders of AdTheorent Class A, Class B, and Class C membership interests issued and outstanding immediately prior to the effective time of the Business Combination will be reduced by the number of MCAP options issued to holders of AdTheorent Class C membership interests. Such reduction has been incorporated into the estimated share amounts contained in this proxy statement/prospectus.

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The Earn-Out Consideration, if payable by MCAP pursuant to the terms in the Business Combination Agreement, may take the form of (i) New MCAP Stock valued at $14.00 per share, (ii) cash, or (iii) a combination of New MCAP Stock valued at $14.00 per share and cash.

​

The “Illustrative Maximum Redemption Scenario” assumes that MCAP Public Stockholders exercise redemption rights with respect to 44% of the outstanding shares of Class A Common Stock. This scenario assumes that 13,769,947 shares of Class A Common Stock are redeemed for an aggregate payment of approximately $137.7 million from the Trust Account, which is the maximum amount of redemptions, without a shortfall of cash, while still satisfying the “Aggregate Cash Consideration” condition to the consummation of the Business Combination. Although not reflected in the illustrative maximum redemption scenario, if redemptions exceed 44%, to the extent there is a shortfall of available cash to pay at least $140.0 million of Aggregate Cash Consideration to AdTheorent’s members and thus satisfy the Aggregate Cash Consideration closing condition, which can only be waived by AdTheorent members in their sole discretion, MCAP has the option under the BCA, in its sole discretion, to make up such shortfall by (i) raising additional funds in a private investment in public equity (“PIPE”) and applying such funds to such shortfall, (ii) causing a portion of AdTheorent’s indebtedness to remain outstanding and applying any funds which would

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otherwise have been applied towards paying off such indebtedness to such shortfall, (iii) requiring AdTheorent or an AdTheorent subsidiary to incur additional indebtedness in an amount not to exceed such shortfall upon commercially reasonable terms mutually agreed upon by MCAP and AdTheorent, each acting in good faith, and applying any such funds to such shortfall, and/or (iv) using a portion of the Balance Sheet Funding Amount and applying any such funds to such shortfall. The shortfall can be resolved using solely one option or a combination of the aforementioned options. If redemptions are 57% or higher, there would be insufficient cash in trust to satisfy the Available Cash closing condition, which can only be waived by AdTheorent members in their sole discretion. In the event redemptions are higher than 57% and AdTheorent members elect to waive the Available Cash closing condition, the transaction could still be consummated if the parties are able to arrange for financing through one or a combination of the levers described above to make up for the shortfall of available cash to pay at least $140.0 million in Aggregate Cash Consideration to AdTheorent’s members, or if AdTheorent members agree to waive or lower the Aggregate Cash Consideration closing condition. Since these scenarios would require the waiver of the AdTheorent members, have not been negotiated and would require the parties to identify sources of financing that either may not be available or may not be available on terms that are acceptable, these scenarios have not been considered in the Illustrative Maximum Redemptions scenario. However, if redemptions exceed 57% and the transaction is still consummated, the resulting impact could be materially different from what is being disclosed in the Illustrative Maximum Redemptions scenario. See Note 2 to “Notes to Unaudited Pro Forma Condensed Combined Financial Information” for further description of the Illustrative Maximum Redemption scenario and a sensitivity analysis showing the impact if redemptions exceed the level shown in this scenario and the transaction is still consummated. There can be no assurance regarding which scenario will be closest to the actual results.

In addition, upon consummation of the Business Combination, and giving effect to the Sponsor’s forfeiture of 551,096 Private Placement Warrants, there will be outstanding an aggregate of 10,541,667 Public Warrants and 5,432,237 Private Placement Warrants held by our Sponsor (551,096 of which will be subject to escrow and forfeiture unless certain earn-out targets are achieved as set forth in the BCA). Each of our outstanding whole warrants is exercisable commencing 30 days following the Closing, for one share of MCAP Common Stock. Therefore, as of the date of this proxy statement/prospectus, if we assume that each outstanding whole warrant is exercised and one share of MCAP Common Stock is issued as a result of such exercise, with payment to MCAP of the exercise price of $11.50 per whole warrant for one whole share, our fully-diluted share capital would increase by a total of 15,973,904 shares, with approximately $183.7 million paid to us to exercise the warrants, assuming cash exercise.

The numbers of shares and percentage interests set forth in the above table under either redemption scenario do not take into account (i) potential future exercises of up to 10,541,667 Public Warrants and up to 5,432,237 Private Placement Warrants (551,096 of which are to be held in escrow subject to earn-out targets), which will remain outstanding immediately following the Business Combination and may be exercised thereafter at an exercise price of $11.50 (commencing 30 days after the Closing of the Business Combination), (ii) 598,875 Founder Shares owned by the Sponsor but held in escrow subject to the achievement of earn-out targets as described in the BCA, (iii) 8,375,241 shares issuable upon the exercise of outstanding options to purchase shares of AdTheorent membership interests, (iv) up to 10,131,638 shares issuable pursuant to the AdTheorent 2021 Long-Term Incentive Plan, (v) up to 2,026,328 shares issuable pursuant to the AdTheorent 2021 Employee Stock Purchase Plan or (vi) warrants to purchase up to 1,000,000 shares if the Sponsor makes a working capital loan prior to the closing of the Business Combination in an amount up to $1,500,000 (no such loans have been made to date). The exercise, issuance or vesting of any of these shares could have a dilutive effect on those of our stockholders who do not elect to redeem their shares. If all such shares were issued immediately after the Business Combination, based on the number of issued and outstanding shares of MCAP Common Stock and AdTheorent Capital Stock on September 30, 2021, and based on the MCAP Common Stock expected to be issued in the Business Combination and the PIPE Financing, non-redeeming Public Stockholders, as a group, would own:

If the actual facts are different than the assumptions set forth above, the share numbers set forth above will be different. For more information, please see the section entitled “Unaudited Pro Forma Condensed Combined Financial Information.”

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Any request for redemption, once made by a holder of Public Shares, may be withdrawn at any time prior to the time the vote is taken with respect to the Business Combination Proposal at the Stockholders Meeting. If you deliver your shares for redemption to MCAP’s transfer agent and later decide prior to the Stockholders Meeting not to elect redemption, you may request that MCAP’s transfer agent return the shares (physically or electronically). You may make such request by contacting MCAP’s transfer agent at Continental Stock Transfer & Trust Company, 1 State Street, 30th Floor, New York, NY 10004, Attention Mark Zimkind. You may have to give such instructions through your broker if your Public Shares are held by the broker in street name.

Any written demand of redemption rights must be received by MCAP’s transfer agent at least two business days prior to the vote taken on the Business Combination Proposal at the Stockholders Meeting. No demand for redemption will be honored unless the holder’s stock has been delivered (either physically or electronically) to the transfer agent.

If you are a holder of Public Shares (including through the ownership of MCAP Units) and you exercise your redemption rights, it will not result in the loss of any MCAP Warrants that you may hold (including those contained in any MCAP Units you hold). Your MCAP Warrants will become exercisable to purchase one share of MCAP Common Stock for a purchase price of $11.50 beginning the later of 30 days after consummation of the Business Combination or 12 months from the closing of the IPO.

For a more detailed discussion of the material U.S. federal income tax consequences of your redemption rights, see the section entitled “Material U.S. Federal Income Tax Considerations of the Redemption Rights and the Business Combination.”

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With respect to the obligations of AdTheorent, among others:

For a summary of the conditions that must be satisfied or waived prior to completion of the Business Combination, see the section entitled, “Proposal No. 1 — The Business Combination Proposal — The Business Combination Agreement — Conditions to Closing the Business Combination.”

If, as a result of the termination of the Business Combination Agreement or otherwise, MCAP is unable to complete a business combination by March 2, 2023 (subject to any applicable extension), MCAP’s amended and restated certificate of incorporation provides that MCAP will: (i) cease all operations except for the purpose of winding up, (ii) as promptly as reasonably possible but not more than ten business days thereafter, redeem 100% of the outstanding Public Shares, at a per share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including any interest not previously released to MCAP but net of taxes payable, divided by the number of then outstanding Public Shares, which redemption will completely extinguish Public Stockholders’ rights as stockholders (including the right to receive further liquidation distributions, if any), subject to applicable law, and (iii) as promptly as reasonably possible following such redemption, subject to the approval of MCAP’s remaining stockholders and The MCAP Board, dissolve and liquidate, subject (in the case of (ii) and (iii) above) to our obligations under Delaware law to provide for claims of creditors and the requirements of other applicable law. See the sections entitled “Risk Factors — MCAP may not be able to consummate an initial business combination within the required time period, in which case it would cease all operations except for the purpose of winding up and it would redeem the Public Shares and liquidate” and “— MCAP’s stockholders may be held liable for claims by third parties against MCAP to the extent of distributions received by them.” The Sponsor has waived any right to any liquidation distribution with respect to the Founder Shares (such waiver entered into in connection with MCAP’s IPO for which the Sponsor received no additional consideration).

In the event of liquidation, there will be no distribution with respect to outstanding MCAP Warrants. Accordingly, the MCAP Warrants will expire worthless.

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For a description of the conditions to the completion of the Business Combination, see the section entitled “The Business Combination Agreement — Conditions to Closing.”

As a registered stockholder, you received a proxy card from Broadridge Financial Solutions, Inc., which contains instructions on how to attend the Stockholders Meeting in person online, including the URL address, along with your 16-digit meeting control number. You will need the 16-digit meeting control number that is printed on your proxy card to enter the Stockholders Meeting. If you do not have your 16-digit meeting control number, contact Broadridge Financial Solutions, Inc., at (833) 501-4817. MCAP recommends that you log in at least 15 minutes before the Stockholders Meeting to ensure you are logged in when the Stockholders Meeting starts.

If your shares are held in “street name,” you may attend the Stockholders Meeting. You will need to contact you will need to obtain a proxy form from the institution that holds your shares and follow the instructions included on that form regarding how to instruct your broker to vote your shares.

You Can Vote By Signing and Returning the Enclosed Proxy Card. If you vote by proxy card, your “proxy,” whose name is listed on the proxy card, will vote your shares and/or your warrants as you instruct on the proxy card. If you sign and return the proxy card but do not give instructions on how to vote your shares, your shares will be voted as recommended by the MCAP Board “FOR” the Business Combination Proposal, the Charter Amendment Proposal, the Advisory Charter Proposals, the Election of Directors Proposal, the Long-Term Incentive Plan Proposal, the ESPP Proposal and the Nasdaq Proposal. Only holders of Founder Shares may vote for the election of each of the directors pursuant to the Director Election Proposal.

You Can Attend the Stockholders Meeting and Vote via Live Webcast. If you choose to participate in the Stockholders Meeting, you can vote your shares electronically during the Stockholders Meeting via live webcast by visiting www.virtualshareholdermeeting.com/MACQ2021SM and using the 16-digit control number included on your proxy card or voting instruction form. MCAP recommends that you log in at least 15 minutes before the Stockholders Meeting to ensure you are logged in when the Stockholders Meeting starts.

If your shares are held in “street name” or are in a margin or similar account, you should contact your broker to ensure that votes related to the shares you beneficially own are properly counted. If you wish to attend the Stockholders Meeting and vote in person via the live webcast and your shares are held in “street name,” you must obtain a legal proxy from your broker, bank or nominee. That is the only way MCAP can be sure that the broker, bank or nominee has not already voted your shares.

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“FOR” the Business Combination Proposal;

“FOR” the Charter Amendment Proposal;

“FOR” each of the Advisory Charter Proposals;

“FOR” the election of each of the directors pursuant to the Director Election Proposal;

“FOR” the Long-Term Incentive Plan Proposal;

“FOR” the ESPP Proposal;

“FOR” the Nasdaq Proposal; and

“FOR” the Stockholder Adjournment Proposal, if it is presented at the Stockholders Meeting.

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The Sponsor invested an aggregate of $9,000,000 in MCAP, comprised of the $25,000 purchase price for the Founder Shares and the $8,975,000 purchase price for the Private Placement Warrants. Assuming a trading price of $8.00 per share upon consummation of the initial business combination, the 7,906,250 shares of Post-Combination Company common stock that the Sponsor and MCAP’s independent directors holding Founder Shares would own upon completion of the initial business combination would have an aggregate implied value of $63,250,000. As a result, even if the trading price of the Post-Combination Company common stock significantly declines, the value of the Founder Shares held by the Sponsor and independent directors will be significantly greater than the amount the Sponsor paid to purchase such shares. In addition, the Sponsor could potentially recoup its entire investment, inclusive of its investment in the Private Placement Warrants, even if the trading price of the Post-Combination Company common stock after the initial business combination is as low as $1.14 per share. As a result, the Sponsor and independent directors holding Founder Shares are likely to earn a substantial profit on their investment in us upon disposition of shares of Post-Combination Company common stock even if the trading price of the Post-Combination Company common stock declines after we complete our initial business combination. The Sponsor and independent directors holding Founder Shares may therefore be economically incentivized to complete an initial business combination with a riskier, weaker-performing or less-established target business, or on terms less favorable to the Public Stockholders, rather than liquidating MCAP.

Members of our Sponsor or their affiliates have committed to purchase an aggregate of 2,650,000 PIPE Shares at a price of $10.00 per share contingent on the Closing of the Business Combination. Such shares, if issued and outstanding, would have an aggregate market value of $26.3 million based on the last sale price of $9.94 per share on Nasdaq on December 1, 2021. See “Certain Agreements Related to the Business Combination — Subscription Agreements.”

Certain officers and directors of MCAP also participate in arrangements that may be argued to provide them with other interests in the Business Combination that are different from yours, including, among others, arrangements for the continued service as directors of the Post-Combination Company.

In addition, the Sponsor and many of MCAP’s officers and directors are affiliated with Monroe Capital LLC. Funds affiliated with Monroe Capital LLC own approximately 2.5% of the fully diluted equity of AdTheorent and have issued debt to AdTheorent with outstanding principal amount of approximately $24.4 million as of September 30, 2021, which debt will be repaid by AdTheorent as a condition to the closing of the Business Combination. Such loans have been outstanding since December 22, 2016 and bear interest equal to the greater of 0.5% or the one-month London Interbank Offered Rate (“LIBOR”), plus 8.5%, per annum. For more information on potential conflicts of interest, see “Certain Relationships and Related Person Transactions.”

These interests, among others, may influence or have influenced the Sponsor and the officers and directors of MCAP and AdTheorent to support or approve the Business Combination. See “Risk Factors — Risks Related to the Domestication and the Business Combination — Some of MCAP’s officers and directors may have conflicts of interest that may influence or have influenced them to support or approve the Business Combination without regard to your interests or in determining whether AdTheorent is appropriate for MCAP’s initial business combination.”

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SUMMARY HISTORICAL FINANCIAL INFORMATION OF MCAP

The following table sets forth selected historical financial data derived from MCAP’s unaudited financial statements as of and for the nine months ended September 30, 2021 and the audited financial statements as of December 31, 2020 and for the period from November 12, 2020 (inception) through December 31, 2020, each of which is included elsewhere in this proxy statement/prospectus. Such financial information should be read in conjunction with the audited financial statements and related notes included elsewhere in this proxy statement/prospectus.

The historical results presented below are not necessarily indicative of the results to be expected for any future period. You should carefully read the following selected financial information in conjunction with the section entitled “MCAP Management’s Discussion and Analysis of Financial Condition and Results of Operations” and MCAP’s financial statements and the related notes appearing elsewhere in this proxy statement/prospectus.

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SUMMARY HISTORICAL CONSOLIDATED FINANCIAL INFORMATION OF ADTHEORENT

The following table sets forth selected historical financial data derived from AdTheorent’s unaudited financial statements as of and for the nine months ended September 30, 2021 and the audited financial statements for the years ended December 31, 2020 and 2019, each of which is included elsewhere in this proxy statement/prospectus. Such financial information should be read in conjunction with the audited financial statements and related notes included elsewhere in this proxy statement/prospectus.

The historical results presented below are not necessarily indicative of the results to be expected for any future period. You should carefully read the following selected financial information in conjunction with the section entitled “AdTheorent Management’s Discussion and Analysis of Financial Condition and Results of Operations” and AdTheorent’s financial statements and the related notes appearing elsewhere in this proxy statement/prospectus.

Consolidated Statements of Operations Data: