SecProbe.io

April 23, 2019
John West
Chief Executive Officer
Personalis, Inc.
1330 O’Brien Drive
Menlo Park, CA 94025
Re:Personalis, Inc.
Draft Registration Statement on Form S-1
Submitted March 27, 2019
CIK No. 0001527753
Dear Mr. West:
            We have reviewed your 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.
Draft Registration Statement on Form S-1 submitted March 27, 2019
General
1.Please supplementally provide us with copies of all written communications, as defined in
Rule 405 under the Securities Act, that you, or anyone authorized to do so on your behalf,
present to potential investors in reliance on Section 5(d) of the Securities Act, whether or
not they retain copies of the communications
Use of Proceeds, page 63
2.Please state the approximate amount of proceeds you intend to use for each purpose
listed.  See Item 504 of Regulation S-K.

 FirstName LastNameJohn West
 Comapany NamePersonalis, Inc.
 April 23, 2019 Page 2
 FirstName LastNameJohn West
Personalis, Inc.
April 23, 2019
Page 2
Management's Discussion and Analysis of Financial Condition and Results of Operations
Results of Operations, page 77
3.We note your revenues increased 302% from 2017 to 2018.  You state that this increase in
revenues was primarily due to an increase in the volume of samples you tested in relation
to the sequencing and data analysis services you provided to our customers.  Please
discuss in greater detail the underlying reasons for the material increase in revenues, such
as the reasons for in the increase in the volume of samples tested.  Additionally, if
applicable, disclose whether the reasons for the change is a known trend that you
reasonably expect will have a material favorable impact on your revenues.  See Item
303(a)(3) of Regulation S-K.
Principal Stockholders, page 148
4.Please disclose the the address for each 5% beneficial owner.  See Item 403(a) of
Regulation S-K.
Note 2 – Summary of Significant Accounting Policies
Fair Value of Common Stock, page F-13
5.We may have additional comments on your accounting for equity issuances including the
stock options and other share-based compensation. Once you have an estimated offering
price, please provide us an analysis explaining the reasons for the differences between
recent valuations of your common stock leading up to the IPO and the estimated offering
price.
Note 3 - Revenues
Contract Assets and Liabilities, page F-16
6.We note that you received large amounts of deposits from customers in each of the years
presented and that the balances of your contract liabilities have grown from $5.6 million
as of January 1, 2017 to $42.9 million as of December 31, 2018.  We also note your
disclosure on page 13, that $37.3 million of the balance at December 31, 2018 relates to
one customer.  Please address the following points:
•Tell us how you considered the guidance in ASC paragraphs 606-10-32-15 through 19
in determining the transaction price in these contracts and whether a significant
financing component exists.
•Explain to us the substantive business purpose of the large advance payments.
•Tell us how you considered disclosing the growing balances as a potential trend that
may impact your cash from operations in future periods in your discussion of liquidity
and capital resources.

 FirstName LastNameJohn West
 Comapany NamePersonalis, Inc.
 April 23, 2019 Page 3
 FirstName LastName
John West
Personalis, Inc.
April 23, 2019
Page 3
Undertakings, page II-4
7.Please add the undertakings required by Item 512(a)(5)(ii) and Item 512(a)(6) of
Regulation S-K. Item 512(a)(5)(ii) is required for any prospectus filed in reliance on Rule
430C and Item 512(a)(6) is required for any offering that involves an initial distribution of
securities pursuant to Rule 159A.  For guidance, refer to Securities Act Rules Compliance
and Disclosure Interpretation, Question 229.01.
Exhibits
8.Please file the Convertible Promissory Note agreements identified on page 146 as
exhibits.  See Item 601(b)(10) of Regulation S-K.
            You may contact James Giugliano at 202-551-3319 or Craig Arakawa at 202-551-3650 if
you have questions regarding comments on the financial statements and related matters.  Please
contact Michael Killoy at 202-551-7576 or Brigitte Lippmann at 202-551-3713 with any other
questions.
Sincerely,
Division of Corporation Finance
Office of Beverages, Apparel and
Mining
cc:       Peter Mandel