Company: ADP
Filing Date: 2025-05-07
Form Type: 424B2
Source: 0001193125-25-114878
Chunk: 44

Company: AUTOMATIC DATA PROCESSING INC
Filing Date: 2025-05-07
Form: 424B2
Chunk 44
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. The validity of the Notes and certain matters pertaining to the Notes will be passed upon for ADP by Davis Polk & Wardwell LLP, New York, New York, and for the underwriters by Simpson Thacher & Bartlett LLP, New York, New
York.

EXPERTS

The financial statements of Automatic Data Processing, Inc. as of June 30, 2024 and 2023, and for each of the three years in the period
ended June 30, 2024, incorporated by reference in this prospectus by reference to Automatic Data Processing, Inc.’s annual report on Form 10-K for the year ended June 30, 2024, and the
effectiveness of Automatic Data Processing, Inc.’s internal control over financial reporting, have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports. Such financial
statements are incorporated by reference in reliance upon the reports of such firm given their authority as experts in accounting and auditing.

S-33

PROSPECTUS

Automatic Data Processing, Inc.

Debt Securities

We may offer debt securities from time to time. Specific terms of these securities will be provided in supplements to this prospectus. You
should read this prospectus and any supplement carefully before you invest.

Investing in these securities involves certain risks. See “Risk Factors” beginning on page 17 of our annual report on Form 10-Kfor the year ended June 30, 2024, which is incorporated by reference herein, as well as in any other recently filed quarterly or current reports. The prospectus supplement applicable to each series of securities we offer may contain a discussion of additional risks applicable to an investment in us and the securities we are offering under that prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or
determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus may not
be used to sell securities unless accompanied by a prospectus supplement.

The date of this prospectus is September 4, 2024

We have not authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus, any accompanying prospectus supplement or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. We take no responsibility for, and can provide no assurance as to the reliability of, any other