UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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☐	Definitive Proxy Statement
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☐	Soliciting material Pursuant to §240.14a-12

Automatic Data Processing, Inc.

(Name of Registrant as Specified In Its Charter)

William A. Ackman

Veronica M. Hagen

V. Paul Unruh

Pershing Square Capital Management, L.P.

PS Management GP, LLC

Pershing Square, L.P.

Pershing Square II, L.P.

Pershing Square International, Ltd.

Pershing Square Holdings, Ltd.

Pershing Square VI Master, L.P.

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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September 15, 2017

Dear Members of the Board,

One of the hallmarks of good corporate governance in contested elections is the use of a “universal proxy card,” which allows stockholders to vote on one card for any combination of nominees from the company’s or Pershing Square’s slate. The use of a universal proxy card helps to preserve a level playing field allowing stockholders to vote for the candidates they believe are most qualified, regardless of whether they are nominated by the company or Pershing Square or which proxy card is utilized in exercising the right to vote. The Council of Institutional Investors supports universal proxies and has enumerated its views in an FAQ which can be found here:

http://www.cii.org/files/issues_and_advocacy/board_accountability/universal%20proxy/Universal%20Proxy%20FAQ%2011-2-16%20final.pdf

In order to give shareholders the opportunity to use a universal proxy card, we are required to obtain permission from the company’s nominees in order to list them in our proxy statement. Therefore, we hereby request that the company arrange for its nominees to provide their consent to being named in the Pershing Square proxy statement and to serve on the board if elected. Pershing Square is, of course, willing to arrange for a reciprocal arrangement with respect to its nominees.

We understand that ADP may have already sent proxy cards to stockholders and that there may be other details that we and Broadridge Financial Solutions may need to work through in order to implement this approach. We are confident that we can work together to resolve these ministerial issues. We note that ADP will most assuredly be sending stockholders a number of additional proxy cards prior to the annual meeting, and nothing would preclude the company from including a new, universal proxy card in those mailings.

We believe that it is incumbent upon Pershing Square and the company to pursue this approach for the benefit of all stockholders who via use of a universal proxy card would be afforded the opportunity to vote for the combination of candidates of their choice.

We look forward to your prompt reply.

Sincerely,

/s/ William A. Ackman

William A. Ackman

CERTAIN INFORMATION CONCERNING THE PARTICIPANTS

Pershing Square Capital Management, L.P. (“Pershing Square”) and certain of its affiliated funds have filed with the Securities and Exchange Commission (the “SEC”) a definitive proxy statement and accompanying GOLD proxy card to be used to solicit proxies in connection with the upcoming annual meeting of stockholders (the “Annual Meeting”) of Automatic Data Processing, Inc. (the “Company”) and the election of a slate of director nominees at the Annual Meeting (the “Solicitation”). Stockholders are advised to read the proxy statement and any other documents related to the Solicitation because they contain important information, including information relating to the participants in the Solicitation. These materials and other materials filed by Pershing Square with the SEC in connection with the Solicitation are available at no charge on the SEC’s website at http://www.sec.gov. The definitive proxy statement and other relevant documents filed by Pershing Square with the SEC are also available, without charge, by directing a request to Pershing Square’s proxy solicitor, D.F. King & Co., Inc., 48 Wall Street, 22nd Floor, New York, New York 10005 (Call Collect: (212) 269-5550; Call Toll Free: (866) 342-1635) or email: ADP@dfking.com.

William A. Ackman, Veronica M. Hagen, V. Paul Unruh, Pershing Square, PS Management GP, LLC (“PS Management”), Pershing Square, L.P., Pershing Square II, L.P., Pershing Square International, Ltd., Pershing Square Holdings, Ltd. and Pershing Square VI Master, L.P. may be deemed “participants” under SEC rules in the Solicitation. William A. Ackman, Pershing Square and PS Management may be deemed to beneficially own the equity securities of the Company described in Pershing Square’s statement on Schedule 13D initially filed with the SEC on August 7, 2017 (the “Schedule 13D”), as it may be amended from time to time. Except as described in the Schedule 13D or the definitive proxy statement, none of the individuals listed above has a direct or indirect interest, by security holdings or otherwise, in the Company or the matters to be acted upon, if any, in connection with the Annual Meeting.