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

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

(Rule 13d-101)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT

TO § 240.13d-1(a) AND AMENDMENTS THERETO FILED

PURSUANT TO § 240.13d-2(a)

Under the Securities Exchange Act of 1934

(Amendment No. 4)*

Automatic
Data Processing, Inc.

(Name of Issuer)

Common Stock, par value $0.10 per share

(Title of Class of Securities)

053015103

(CUSIP Number)

Stephen Fraidin, Esq.

Steve Milankov, Esq.

Pershing Square Capital Management, L.P.

888 Seventh Avenue, 42nd Floor

New York, New York 10019

(212) 813-3700

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

March 12, 2018

(Date of Event which Requires Filing of this Statement)

If the filing person has
previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e),
240.13d-1(f) or 240.13d-1(g), check the following box.  ☐

Note: Schedules filed in paper format shall
include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

CUSIP No. 053015103

CUSIP No. 053015103

CUSIP No. 053015103

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.

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 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 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.

Item 7 of the Original Schedule 13D is hereby amended
and supplemented by adding a reference to the following exhibit:

SIGNATURE

After reasonable inquiry and to the best of each of the undersigneds knowledge and belief, each of the undersigned certify that the
information set forth in this statement is true, complete and correct.

Dated: March 13, 2018

INDEX TO EXHIBITS