February 14, 2020

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

       Re: Datto Holding Corp.
           Amendment No. 1 to Draft Registration Statement on Form S-1
           Submitted January 31, 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. References to our prior comments refer to our letter dated January
14, 2020.

Amendment No. 1 to Confidential Filing on Form S-1

Prospectus Summary, page 1

1.     We note your revised disclosures on page 92 in response to prior comment
1.
       Please disclose the percentage of annual recurring revenue generated
from customers with
       greater than $100,000 in ARR where you first discuss this metric in the
filing.
Use of Proceeds, page 63

2.     We note your responses to prior comments 7 and 20 regarding your $600
million Credit
       Agreement that will be repaid, in part, by offering proceeds. While your
$600 million
       Credit Agreement was part of an April 2019 refinancing of a prior
December 2017 $520
       million Term Loan, please clarify whether the initial Term Loan was used
by affiliates of
 Tim Weller
Datto Holding Corp.
February 14, 2020
Page 2
         Vista to acquire Datto, Inc. Further, please disclose in this section
the role of your
         underwriters with the current $600 million Credit Agreement.
Management's Discussion and Analysis of Financial Condition and Results of
Operations
Key Performance Metrics, page 75

3.       We note your revised disclosures in response to prior comment 9. In an
effort to provide
         support for including monthly contracts in your ARR calculations and
to add context to
         this metric, please disclose the percentage of revenue from monthly
contracts that are
         included in such calculations. Also, disclose the estimated gross
dollar retention rate for
         all contracts along with management's assertions that while you are
not able to precisely
         calculate gross dollar-retention rate solely for monthly
subscriptions, you do not believe
         the attrition for month-to-month subscriptions is materially higher
than that of term-based
         subscriptions. Lastly, please further explain your reference to the
net dollar retention rate
         as support for including monthly contracts in your ARR calculations as
this measure does
         not capture cancellations during the current period for any contracts
that were outstanding
         as of the last day of the prior reporting period.
Components of Results of Operations, page 76

4.       Please further explain your statement that device revenue will
continue to decrease as a
         percentage of overall revenue as you continue to shift from selling
network devices on a
         standalone basis to packaging network devices with cloud-based
management software
         and services as part of a recurring subscription. Clarify whether you
currently provide, or
         intend to provide, subscriptions arrangements in which devices are
combined with the
         subscription services. Also, explain whether this impacts your current
accounting policies
         where you state that devices are a separate performance obligation. To
the extent, you
         have arrangements in which the devices and services are considered one
performance
         obligation, please tell us the accounting considered and the amount of
revenue recognized
         from such arrangements for all periods presented.
Business, page 91

5.     We note your revised disclosures in response to prior comment 11 as it
relates to the
       Autotask acquisition. Please also disclose the terms of the Vista
Acquisition and
       specifically address the consideration transferred and the basis for the
significant premium
FirstName LastNameTim Weller
       paid as indicated in your response to prior comment 22. Refer to Item
101(a)(1) of
Comapany NameDatto Holding Corp. for us the consideration paid in this
transaction, including
       Regulation S-K. Also, describe
February 14, 2020 of shares issued and how such shares were valued.
       the number Page 2
FirstName LastName
 Tim Weller
FirstName LastNameTim Weller
Datto Holding Corp.
Comapany NameDatto Holding Corp.
February 14, 2020
Page 3
February 14, 2020 Page 3
FirstName LastName
       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, Attorney-
Advisor, at (202) 551-3297 or Larry Spirgel, Office Chief, at (202) 551-3815
with any other
questions.



                                                          Sincerely,

                                                          Division of
Corporation Finance
                                                          Office of Technology
cc:      Robert E. Goedert, P.C.