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                              September 22, 2020

       Tim Weller
       Chief Executive Officer
       Datto Holding Corp.
       101 Merritt 7
       Norwalk, CT 06851

                                                        Re: Datto Holding Corp.
                                                            Amendment No. 3 to
Draft Registration Statement on Form S-1
                                                            Submitted September
4, 2020
                                                            CIK No. 0001724570

       Dear Mr. Weller:

             We have reviewed your amended draft 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 providing the requested
information and either submitting
       an amended draft registration statement or publicly filing your
registration statement on
       EDGAR. 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 the information you provide in response to these
comments and your
       amended draft registration statement or filed registration statement, we
may have additional
       comments.

       Amendment No. 3 to Draft Registration Statement on Form S-1

       Graphics, page 1

   1.                                                   It is not clear from
your graphics in the forepart of your registration statement whether the
                                                        Last Twelve Months Net
Income of $5 million represents the period from June 30, 2019
                                                        through June 30, 2020.
Please also clarify that you actually generated a net loss of $31.2
                                                        million for the twelve
months ended for the fiscal year ended December 31, 2019 to
                                                        balance your
disclosure. Further, please specify the point in time metrics that are dated as
                                                        of June 30, 2020, such
as your Dollar-based net retention ratio.

   2.                                                   The chart at the
forefront of your document depicting your annual recurring revenue from
                                                        partner cohorts is not
accompanied by sufficient explanation. For example, it is not clear
 Tim Weller
Datto Holding Corp.
September 22, 2020
Page 2
      what dollar amounts are being measured. Please revise to provide clearer
guidance of
      what is being depicted.
Notes to Consolidated Financial Statements
Note 12. Stock-Based Employee Compensation, page F-32

3.    Please provide us with an updated breakdown of all options granted
through June 30,
      2020 as well as any grants made subsequent to the most recent balance
sheet date, and
      include the fair value of the underlying common stock at the date of such
grants as
      determined by your board of directors. To the extent there were any
significant
      fluctuations in the fair value prices from period-to-period, describe for
us the factors that
      contributed to these fluctuations, including any intervening events
within the company or
      changes in your valuation assumptions or methodology, underlying common
stock used to
      value such awards as determined by your board of directors.
        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 Edwin
Kim,
AttorneyAdvisor, at (202) 551-3297 or Larry Spirgel, Office Chief, at (202)
551-3815 with any
other questions.



                                                            Sincerely,
FirstName LastNameTim Weller
                                                            Division of
Corporation Finance
Comapany NameDatto Holding Corp.
                                                            Office of
Technology
September 22, 2020 Page 2
cc:       Robert E. Goedert, P.C.
FirstName LastName