Company: ADP
Filing Date: 2025-05-07
Form Type: 424B2
Source: 0001193125-25-114878
Chunk: 5

Company: AUTOMATIC DATA PROCESSING INC
Filing Date: 2025-05-07
Form: 424B2
Chunk 5
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 services to clients; |

| • |     | the pricing of products and services; |

| • |     | the success of our new solutions; |

| • |     | our ability to respond successfully to changes in technology, including artificial intelligence; |

| • |     | compliance with existing or new legislation or regulations; |

| • |     | changes in, or interpretations of, existing legislation or regulations; |

| • |     | overall market, political and economic conditions, including interest rate and foreign currency trends and 
 inflation;                                                                                                 |

| • |     | competitive conditions; |

| • |     | our ability to maintain our current credit ratings and the impact on our funding costs and profitability; |

| • |     | security or cyber breaches, fraudulent acts, and system interruptions and failures; |

| • |     | employment and wage levels; |

| • |     | availability of skilled associates; |

| • |     | the impact of new acquisitions and divestitures; |

| • |     | the adequacy, effectiveness and success of our business transformation initiatives; |

| • |     | the impact of any uncertainties related to major natural disasters or catastrophic events; and |

| • |     | supply-chain disruptions. |

The factors identified above are not exhaustive. ADP disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events, or otherwise, except as required by law. These risks and uncertainties, along with the risk factors discussed under “Item 1A. Risk Factors” in ADP’s most recently filed Annual Report on Form 10-Kand the risk factors under the caption “Risk Factors” in this prospectus supplement and the accompanying prospectus, should be considered in evaluating any forward-looking statements contained herein. S-5

RISK FACTORS Investing in the Notes involves risks. Before making a decision to invest in the Notes, you should carefully consider the risks described under “Risk Factors” in Item 1A. of our Annual Report on Form 10-Kfor the fiscal year ended June 30, 2024, which is incorporated by reference into this prospectus supplement and the accompanying prospectus, as well as the risks set forth below. See “Where You Can Find More Information” in the accompanying prospectus. The indenture governing the Notes does not contain financial covenants or meaningful restrictions on us or our subsidiaries. Neither we nor any of our subsidiaries are restricted from incurring additional debt or other liabilities under the indenture. We