DEFA14A

SCHEDULE 14A(Rule 14a-101)INFORMATION REQUIRED IN PROXY STATEMENTProxy Statement Pursuant to Section 14(a) ofthe Securities Exchange Act of 1934(Amendment No. )

Filed by the Registrant ý

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐ Definitive Proxy Statement

☒ Definitive Additional Materials

☐ Soliciting material Pursuant to Rule 14a-12

AUTOMATIC DATA PROCESSING, INC.

(Name of Registrant as Specified In Its Charter)

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

PAYMENT OF FILING FEE (Check the appropriate box):

ý No fee required.

☐ Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

1) Title of each class of securities to which transaction applies:

2) Aggregate number of securities to which transaction applies:

3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (Set forth the amount on which the filing fee is calculated and state how it was determined):

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☐ Fee paid previously with preliminary materials.

☐ Check box if any part of the fee is offset as provided by Exchange Act Rule 0‑11(a)(2) and identify the filing for which the offsetting fee was paid previously. Identify the previous filing by registration statement number, or the Form or Schedule and the date of its filing.

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The press release attached hereto as Exhibit 1 may be provided to stockholders of Automatic Data Processing, Inc.

EX-99.1

EXHIBIT 1

ADP FILES DEFINITIVE PROXY MATERIALS

ROSELAND, NJ, September 7, 2017 – ADP (NASDAQ: ADP) today announced that it has filed definitive proxy materials with the Securities and Exchange Commission in connection with ADP’s 2017 Annual Meeting of Stockholders to be held on November 7, 2017.  Stockholders of record at the close of business on September 8, 2017 will be entitled to vote at the Annual Meeting.

ADP’s Board unanimously recommends that ADP stockholders vote to re-elect ADP’s 10 highly qualified and experienced director nominees. You can support the ADP Board by voting the WHITE proxy card. We encourage stockholders to date, sign and return the WHITE proxy card being provided to you, or to use the telephone or Internet method of voting described on the WHITE proxy card.

ADP urges shareholders to discard any gold proxy card from Pershing Square.

Morgan Stanley & Co. and Goldman Sachs are acting as financial advisors and Paul, Weiss, Rifkind, Wharton & Garrison LLP is acting as legal advisor to ADP.

About ADP (NASDAQ: ADP)

Powerful technology plus a human touch. Companies of all types and sizes around the world rely on ADP cloud software and expert insights to help unlock the potential of their people. HR. Talent. Benefits. Payroll. Compliance. Working together to build a better workforce. For more information, visit ADP.com.

The ADP logo, ADP, are registered trademarks of ADP, LLC. ADP A more human resource. is a service mark of ADP, LLC. All other marks are the property of their respective owners.

Copyright © 2017 ADP, LLC. All rights reserved.

ADP-Media

Safe Harbor Statement

This document and other written or oral statements made from time to time by ADP may contain “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Statements that are not historical in nature and which may be identified by the use of words like “expects,” “assumes,” “projects,” “anticipates,” “estimates,” “we believe,” “could,” “is designed to” and other words of similar meaning, are forward-looking statements. These statements are based on management’s expectations and assumptions and depend upon or refer to future events or conditions and are subject to risks and uncertainties that may cause actual results to differ materially from those expressed. Factors that could cause actual results to differ materially from those contemplated by the forward-looking statements or that could contribute to such difference include: ADP's success in obtaining and retaining clients, and selling additional services to clients; the pricing of products and services; compliance with existing or new legislation or regulations; changes in, or interpretations of, existing legislation or regulations; overall market, political and economic conditions, including interest rate and foreign currency trends; competitive conditions; our ability to maintain our current credit ratings and the impact on our funding costs and profitability; security or privacy breaches, fraudulent acts, and system

interruptions and failures; employment and wage levels; changes in technology; availability of skilled technical associates; and the impact of new acquisitions and divestitures. ADP disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. These risks and uncertainties, along with the risk factors discussed under “Item 1A. - Risk Factors” in our Annual Report on Form 10-K should be considered in evaluating any forward-looking statements contained herein.

ADDITIONAL INFORMATION

ADP, its directors and certain of its executive officers may be deemed to be participants in the solicitation of proxies from Company shareholders in connection with the matters to be considered at the Company’s 2017 Annual Meeting. The Company has filed a definitive proxy statement and WHITE proxy card with the U.S. Securities and Exchange Commission (the “SEC”) in connection with any such solicitation of proxies from Company shareholders. COMPANY SHAREHOLDERS ARE STRONGLY ENCOURAGED TO READ THE DEFINITIVE PROXY STATEMENT AND ACCOMPANYING WHITE PROXY CARD AS THEY CONTAIN IMPORTANT INFORMATION. Information regarding the identity of potential participants, and their direct or indirect interests, by security holdings or otherwise, is set forth in the proxy statement and other materials to be filed with the SEC. Shareholders will be able to obtain any proxy statement, any amendments or supplements to the proxy statement and other documents filed by the Company with the SEC for no charge at the SEC’s website at www.sec.gov. The proxy statement and other relevant documents filed by ADP with the SEC are also available, without charge, by directing a request to ADP’s proxy solicitor, Innisfree M&A Incorporated, 501 Madison Avenue, 20th Floor, New York, New York 10022; call toll-free: (877) 750-0510 or call collect: (212) 750-5833. Copies will also be available at no charge at the Company’s website atwww.adp.com.

CONTACTS:

Investors:

Christian Greyenbuhl

(973) 974-7835

Christian.Greyenbuhl@adp.com

Byron Stephen

(973) 974-7896

Byron.Stephen@adp.com

OR

Innisfree M&A Incorporated(877) 750-0510

Media:

Michael Schneider

(973) 974-5678 office

(973) 868-1000 mobile

Michael.Schneider@adp.com

George Sard/Jared Levy/Liz ZaleSard Verbinnen & Co(212) 687-8080

ADP-SVC@sardverb.com