13D Filing: Pershing Square and Automatic Data Processing Inc (ADP)

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This amendment No. 4 (the Amendment No. 4) to Schedule
13D relates to the Schedule 13D filed on August 7, 2017 (the Original Schedule 13D, as amended and supplemented through the date of this Amendment No. 4, the Schedule 13D) by (i) Pershing Square
Capital Management, L.P., a Delaware limited partnership (Pershing Square); (ii) PS Management GP, LLC, a Delaware limited liability company (PS Management); and (iii) William A. Ackman, a citizen of the
United States of America (together with Pershing Square and PS Management, the Reporting Persons) relating to the common stock, par value $0.10 per share (the Common Stock), of Automatic Data Processing, Inc., a
Delaware corporation (the Issuer).

Capitalized terms used but not defined in this Amendment No. 4 shall have the
meetings set forth in the Schedule 13D.

Except as specifically amended by this Amendment No. 4, the Schedule 13D is unchanged.

Item 1.

Security and Issuer

The second and third paragraphs of Item 1 of the Original Schedule
13D is hereby amended and restated in full to read as follows:

The Reporting Persons beneficially own 31,799,042 shares of Common
Stock (the Subject Shares), which number includes: 7,941,957 shares of Common Stock, and 23,857,085 shares underlying listed and over-the-counter
American-style call options.

The Subject Shares represent approximately 7.2% of the outstanding shares of Common Stock based on
443,269,657 shares of Common Stock outstanding as of January 26, 2018 as reported in the Issuers Quarterly Report on Form 10-Q filed on February 1, 2018 for the calendar quarter ended
December 31, 2017.

Item 4.

Purpose of the Transaction

Item 4 of the Original Schedule 13D is hereby amended and
supplemented by adding the following information:

The Reporting Persons on behalf of the Pershing Square Funds sold a net amount of
5,004,633 shares of Common Stock and American-style call options for portfolio management purposes.

Item 5.

Interest in Securities of the Issuer

Item 5 of the Original Schedule 13D is hereby
amended and supplemented by adding the following information:

(a), (b) Information about the number and percentage of shares of
Common Stock beneficially owned by the Reporting Persons is set forth in Item 1, and that information is incorporated by reference herein.

(c) Exhibit 99.10 filed herewith, which is incorporated by reference into this Item 5(c) as if restated in full, describes all of the
transactions in the Common Stock or derivatives relating to Common Stock that were effected in the past 60 days by the Reporting Persons for the benefit of PS and PS International. Except as set forth in Exhibit 99.10 no reportable transactions were
effected by any Reporting Person within the last 60 days.