Company: PAYX
Filing Date: 2025-04-08
Form Type: 424B2
Source: 0001193125-25-075170
Chunk: 9

Company: PAYCHEX INC
Filing Date: 2025-04-08
Form: 424B2
Chunk 9
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 services as they grow; |

| • |     | Software as a service, or “SaaS”, delivery model that reduces total cost of ownership for our clients; 
 and                                                                                                    |

| • |     | Advanced data analytics and artificial intelligence capabilities powered by large data sets. |

We market our solutions through a combination of direct and virtual sales forces and ecommerce solutions supported by various digital lead generation and multi-channel marketing initiatives. Over 50% of our revenues are from solutions other than payroll processing. We were incorporated in Delaware in 1979. Our principal executive offices are located at 911 Panorama Trail South, Rochester, New York 14625-2396 and our principal website address is www.paychex.com. Information on or accessible through our website is not incorporated into this prospectus supplement.

S-1

Proposed Acquisition of Paycor

On January 7, 2025, Paychex, Inc., Skyline Merger Sub., Inc., a Delaware corporation and an indirect wholly owned subsidiary of Paychex,
and Paycor entered into an Agreement and Plan of Merger (the “Merger Agreement”) to acquire Paycor (the “Acquisition”), a leading provider of HCM, payroll and talent software. The closing of the Acquisition is subject to certain
customary closing conditions. Subject to satisfaction of the closing conditions, the Acquisition is expected to close in April 2025.

We
expect to use the net proceeds from this offering to fund the Acquisition, including the payment of related fees and expenses, with any remaining net proceeds for general corporate purposes. The closing of this offering is not conditioned upon the
consummation of the Acquisition. See “Use of Proceeds.”

S-2

The Offering The following description of certain provisions of the notes offered hereby is not complete, does not contain all the information that is important to you and is subject to, and qualified in its entirety by reference to, the information appearing in this prospectus supplement under the caption “Description of Notes” and in the accompanying prospectus under the caption “Description of Debt Securities.”

| Issuer | Paychex, Inc. |

| Securities Offered | $   aggregate principal amount of    % notes due 20 |

| $   aggregate principal amount of   % notes due 20 |

| $   aggregate principal amount of   % notes due 20 |

| Maturity | 20  notes —