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

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This amendment No. 1 (the Amendment No. 1) to Schedule 13D relates
to the Schedule 13D filed on August 7, 2017 (the Original 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. 1 shall have the meetings set forth in the Original Schedule 13D.

Except as specifically amended by this Amendment No. 1, the Original Schedule 13D is unchanged.

Item 1.

Security and Issuer

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

The Reporting Persons beneficially own 36,803,675 shares
of Common Stock (the Subject Shares), which number includes: 8,798,442 shares of Common Stock, and 28,005,233 shares underlying listed and over-the-counter American-style call options.

The Subject Shares represent approximately 8.3% of the outstanding shares of Common Stock based on 444,374,752 shares of Common Stock
outstanding as of July 31, 2017 as reported in the Issuers Annual Report on Form 10-K filed on August 4, 2017 for the fiscal year ended June 30, 2017.

Item 3.

Source and Amount of Funds or Other Consideration

Item 3 of the Original Schedule
13D is hereby amended and supplemented by adding the following information:

On August 29, 2017, early termination of the
waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, was granted with respect to the holdings of shares of Common Stock of PS, PS International, PSH and PS VI.

On August 30, 2017, the Reporting Persons, for the account of PS VI, paid the applicable forward purchase price under the forward
purchase contracts to purchase 4,029,425 shares of Common Stock for a total consideration of $460,867,765. In addition, the Reporting Persons, for the account of PSH, unwound over-the-counter American-style call options referencing 3,002,767 shares
of Common Stock and purchased 3,002,767 shares of Common Stock, the consideration for which is set forth in Exhibit 99.7.

The source of
funding for these transactions was derived from the capital of the respective funds.

Item 4.

Purpose of the Transaction

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

The purpose of the transactions effected on August 30, 2017 was to
acquire voting securities of the Issuer.