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                            October 22, 2021

       Theodore L. Koenig
       Chairman and Chief Executive Officer
       MCAP Acquisition Corporation
       311 South Wacker Drive, Suite 6400
       Chicago, Illinois 60606

                                                        Re: MCAP Acquisition
Corporation
                                                            Amendment No. 1 to
Registration Statement on Form S-4
                                                            Filed October 6,
2021
                                                            File No. 333-259027

       Dear Mr. Koenig:

             We have reviewed your amended registration statement and have the
following
       comments. In some of our comments, we may ask you to provide us with
information so we
       may better understand your disclosure.

              Please respond to this letter by amending your registration
statement and providing the
       requested information. If you do not believe our comments apply to your
facts and
       circumstances or do not believe an amendment is appropriate, please tell
us why in your
       response.

              After reviewing any amendment to your registration statement and
the information you
       provide in response to these comments, we may have additional comments.
Unless we note
       otherwise, our references to prior comments are to comments in our
September 23, 2021 letter.

       Amendment No. 1 to Form S-4 filed October 6, 2021

       Summary of the Proxy Statement/Prospectus
       Organizational Structure, page 7

   1.                                                   Please revise the table
showing the ownership of the combined company after the business
                                                        combination to reflect
the same shareholder groups that are in the organizational diagram.
                                                        In addition, include
within the share ownership of MCAP's Sponsor the amount of shares
                                                        it is purchasing in the
PIPE investment.
 Theodore L. Koenig
FirstName LastNameTheodore
MCAP Acquisition  CorporationL. Koenig
Comapany
October 22,NameMCAP
            2021       Acquisition Corporation
October
Page 2 22, 2021 Page 2
FirstName LastName
Questions and Answers About the Business Combination, page 17

2.       Please revise your Q&As or provide a new Q&A to clarify that, while
all the MCAP
         public shares have redemption rights, you are assuming that no more
than 43% of MCAP
         public shares will be redeemed in your    illustrative maximum
redemption scenario.
         Explain why you have made this assumption and how it specifically
relates to the $140
         million Aggregate Cash Consideration condition. Briefly discuss the
options the company
         has to make up Aggregate Cash Consideration shortfalls if redemptions
exceed 43% of
         public shares. In addition, clarify that up to 57% of public shares
may be redeemed and
         still meet the $258.125 million Available Cash condition. Disclose
that AdTheorant would
         have to waive the Available Cash condition if more than 57% of public
shares are
         redeemed for the business combination to be consummated.
What equity stake will current MCAP stockholders and AdTheorent Stockholders
have in the
Post-Combination Company after the Closing?, page 19

3.       We note your response to prior comment 7. Please revise to disclose
all possible sources
         and extent of dilution that shareholders who elect not to redeem their
shares may
         experience in connection with the business combination. Provide
disclosure of the impact
         of each significant source of dilution, including the amount of equity
held by founders and
         convertible securities, such as warrants retained by redeeming
shareholders, at each of the
         redemption levels detailed in your sensitivity analysis, including any
needed
         assumptions.
Do the Sponsor and MCAP   s officers and directors have any conflicts of
interest that may
influence them to support the Business Combination?, page 26

4.       Please disclose here and on page 120 that the Sponsor will experience
significant financial
         benefits from completing a business combination and may be
incentivized to complete an
         acquisition of a less favorable target company or on terms less
favorable to shareholders
         rather than liquidate. Also disclose that the Sponsor and its
affiliates can earn a positive
         rate of return on their investment, even if other SPAC shareholders
experience a negative
         rate of return in the post-business combination company.
Summary Historical Consolidated Financial Information of AdTheorent
Other Key Operating and Financial Performance Metrics, page 31

5.       We note your response and revised disclosures to prior comments 9 and
23. Please
         address the following:
             Clarify whether there is any amortization or depreciation expense
included within
             platform operations expense. In this regard, SAB Topic 11.B
prohibits a gross profit
             measure that excludes depreciation and amortization expense.
Please revise
             accordingly.
             Revise to describe the type and nature of the expenses added back
in the line item
             "other platform operations."
 Theodore L. Koenig
MCAP Acquisition Corporation
October 22, 2021
Page 3
                Revise to disclose why management believes that presentation of
a non-GAAP gross
              profit measure is useful to investors and, to the extent
material, disclose the additional
              purposes, if any, for which management uses this measure. Refer
to Item
              10(e)(1)(i)(C) and (D) of Regulation S-K.
                Revise the tabular disclosure on pages 32 and 194 to provide
the ratio of GAAP
              Gross Profit as a % of GAAP Revenue prior to the presentation of
Gross Billings less
              TAC as a % of Revenue. Refer to Item 10(e)(1)(i)(A) of Regulation
S-K and
              Question 102.10 of the Non-GAAP C&DIs.
                Revise page 168 to disclose GAAP Gross Profit with equal or
greater prominence to
              Gross Billings Less TAC. Also, revise here to disclose the
percentage change in
              GAAP net income/(loss) for the six months ended June 30, 2021
compared to 2020
              before the percentage increase in Adjusted EBITDA.
                Revise the disclosures on page 173 to present net income as a
percentage of Gross
              Profit before your discussion of EBITDA and Adjusted EBITDA as a
percentage of
              Gross Billings Less TAC.
6.       Please consider renaming the non-GAAP measure of    Gross Billing Less
TAC    to more
         accurately reflect the nature of the measure, such as adjusted gross
profit or contribution
         margin less TAC. In this regard, billings is a common metric that
represents the total
         amounts invoiced and, as such, your reference to billings does not
appear appropriate in
         the context of a gross profit measure. Refer to Item 10(e)(1)(ii)(E)
of Regulation S-K.
Risks Related to the Ownership of AdTheorent Common Stock
AdTheorent's amended and restated certificate of incorporation will include...,
page 65

7.       Please reconcile your disclosure in this risk factor to conform with
the disclosure about
         your exclusive forum provision on pages 247 and 254. In this regard,
we note that the
         disclosure on pages 247 and 254 discusses that the exclusive forum
provision also applies
         to any action arising under the proposed certificate of incorporation,
the post-combination
         company bylaws or any action asserting a claim against the
post-combination company
         governed by the internal affairs doctrine. In addition, the proposed
certificate of
         incorporation designates the federal district courts of the United
States of America as the
         exclusive forum for the resolution of any complaint asserting a cause
of action arising
         under the Securities Act.
Risk Factors
MCAP determined that a material weakness existed in its internal control over
financial
reporting as of March 2, 2021. If MCAP is unable... , page 81
FirstName LastNameTheodore L. Koenig
8.     We note your response and revised disclosure to prior comment 12. Please
amend your
Comapany
       FormNameMCAP
             10-Q for theAcquisition  Corporation
                          fiscal quarter ended June 30, 2021 to appropriately
reflect your
Octoberconclusion that disclosure
        22, 2021 Page   3         controls and procedures were not effective as
of that date.
FirstName LastName
 Theodore L. Koenig
FirstName LastNameTheodore
MCAP Acquisition  CorporationL. Koenig
Comapany
October 22,NameMCAP
            2021       Acquisition Corporation
October
Page 4 22, 2021 Page 4
FirstName LastName
Unaudited Pro Forma Condensed Combined Financial Information
Note 2. Basis of Pro Forma Presentation, page 96

9.       We note your response and revised disclosures to prior comment 14
where you indicate
         that if redemptions are 57% or higher you will be unable to meet the
Available Cash
         necessary to satisfy the conditions of the Business Combination.
Please revise to further
         explain what happens if more than 57% of public shares are redeemed.
In this regard, to
         the extent AdTheorant chooses to waive such condition, clarify whether
the BCA
         stipulates any options to satisfy the shortfall or state, if true,
that such terms have yet to be
         negotiated and could result in significantly different outcomes than
currently disclosed.
3. Adjustments to Unaudited Pro Forma Condensed Combined Financial Information,
page 100

10.      We note your response and revised disclosures to prior comment 15. It
appears the $43.3
         million increase in additional paid-in capital currently labeled as
adjustment (h) actually
         relates to pro forma adjustment (i). Please revise or advise.
Material U.S. Federal Tax Considerations of the Redemption Rights and the
Business
Combination, page 142

11.      We note your response to prior comment 22. Please revise the summary
and risk factor
         disclosure sections to set forth the risks of uncertain tax treatment
of the company mergers
         to investors.
Information About AdTheorent, page 167

12.      We note your response and revised disclosures to prior comment 24.
Since you continue
         to disclose active customers, high-spend clients and the percentage of
2020 revenue
         generated from customers who have been with you since 2017 or earlier,
please further
         revise to describe how these measures are calculated. Additionally,
while we
         acknowledge you do not use these measures to evaluate your business
and operations,
         please tell us and revise to address what measures you do use to
monitor your ability to
         retain and grow customers. In this regard, we note you continue to
disclose on page
         39 that your success is dependent on regularly adding new customers
and increasing
         existing customers' usage, and that per page 172 you consider customer
retention and
         growth to be one of your strengths. Refer to Item 303(a) of Regulation
S-K and SEC
         Release No. 33-10751.
AdTheorent Management's Discussion and Analysis of Financial Condition and
Results of
Operations
Results of Operations, page 188

13.      We note your response and revised disclosure to prior comment 26.
Where a material
         change is attributed to two or more factors, including any offsetting
factors, the
         contribution of each identified factor should be described in
quantified terms. For
 Theodore L. Koenig
MCAP Acquisition Corporation
October 22, 2021
Page 5
      example, you state that growth in revenue between the six-months ended
June 30, 2020
      and 2021 was due to strength in the brand direct customer growth,
expansion of agency
      customer relationships including entry into volume based letters of
understanding as well
      as substantial growth in Video and CTV, but you do not quantify any of
these
      factors. Similarly, you refer to an increase in platform operation costs
due to revenue-
      driven growth, volume-driven increases in hosting costs and hiring-driven
increases in
      personnel costs, but it is unclear how each factor contributed to the
overall increase in
      platform costs. Please revise accordingly. Refer to Item 303(a) of
Regulation S-K and
      Section III.D of SEC Release No. 33-6835.
Selected Quarterly Financial Information, page 194

14.   We note your revised disclosures in response to prior comment 27. Please
further revise
      to explain why you have not presented quarterly information for fiscal
2019 or consider
      including quarterly information for all periods in which financial
statements are provided.
Liquidity and Capital Resources
Cash Flow Summary, page 198

15.   We note your response and revised disclosure to prior comment 28. Please
further revise
      to disclose the period over which you calculated the average days sales
outstanding (DSO)
      range of 76 to 126 days. Also, explain why your DSO has exceeded your
typical payment
      terms of 30 to 60 days for all periods presented, even for those prior to
the pandemic.
        You may contact Brittany Ebbertt, Senior Staff Accountant, at
202-551-3572 or Kathleen
Collins, Accounting Branch Chief, at 202-551-3499 if you have questions
regarding comments
on the financial statements and related matters. Please contact Alexandra
Barone, Staff
Attorney, at 202-551-8816 or Kathleen Krebs, Special Counsel, at 202-551-3350
with any other
questions.



                                                           Sincerely,
FirstName LastNameTheodore L. Koenig
                                                           Division of
Corporation Finance
Comapany NameMCAP Acquisition Corporation
                                                           Office of Technology
October 22, 2021 Page 5
cc:       Jonathan Talcott, Esq.
FirstName LastName