Company: ADP
Filing Date: 2025-05-07
Form Type: 424B2
Source: 0001193125-25-114878
Chunk: 1

Company: AUTOMATIC DATA PROCESSING INC
Filing Date: 2025-05-07
Form: 424B2
Chunk 1
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Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The Notes will be ready for delivery in book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, including Euroclear Bank S.A./N.V. and Clearstream Banking, société anonyme, on or about May 8, 2025. Joint Book-Running Managers

| BofA Securities |     | J.P. Morgan              |     | Morgan Stanley         |
| BNP PARIBAS     |     | Deutsche Bank Securities |     | Wells Fargo Securities |

Co-Managers

| Barclays               |     | MUFG                           |     | PNC Capital Markets LLC    |
| RBC Capital Markets    |     | BMO Capital Markets            |     | US Bancorp                 |
| Fifth Third Securities |     | Siebert Williams Shank         |     | ING                        |
| IMI – Intesa Sanpaolo  |     | HSBC                           |     | Scotiabank                 |
| Academy Securities     |     | BNY Capital Markets            |     | Huntington Capital Markets |
| TD Securities          |     | BOK Financial Securities, Inc. |     | Ramirez & Co., Inc.        |

May 5, 2025

We have not authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus supplement, the accompanying prospectus 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 information that others may give you. This prospectus supplement and the accompanying prospectus are an offer to sell only the Notes, but only under circumstances and in jurisdictions where it is lawful to do so. The information contained in this prospectus supplement, the accompanying prospectus or in any free writing prospectus, as well as information previously filed with the Securities and Exchange Commission (“SEC”) and incorporated herein by reference, is current only as of the date of such information. Our business, financial condition, results of operations and prospects may have changed since that date. References in this prospectus supplement and the accompanying prospectus to the “Company,” “ADP,” “we,” “us,” and “our” refer to Automatic Data Processing, Inc. and its subsidiaries,