Company: PAYX
Filing Date: 2025-04-09
Form Type: 424B2
Source: 0001193125-25-076822
Chunk: 19

Company: PAYCHEX INC
Filing Date: 2025-04-09
Form: 424B2
Chunk 19
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 to do so. In
addition, our ability to repurchase the notes for cash may be limited by law or the terms of any other indebtedness outstanding at the time. Accordingly, we may not be able to satisfy our obligations to repurchase your notes unless we are able to
refinance or obtain consents from the holders of such indebtedness. The failure to make such repurchase would result in a default under the notes and could cause a cross-default or acceleration under certain agreements governing our other
indebtedness.

S-10

USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $4,145.1 million after deducting the underwriting discounts
and our estimated offering expenses.

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.

S-11

CAPITALIZATION The following table sets forth our cash and cash equivalents and capitalization as of February 28, 2025, on an actual basis and an as adjusted basis to reflect the issuance and sale of the notes. You should read this table in conjunction with our unaudited condensed consolidated financial statements and related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” included in our Quarterly Report on Form 10-Qfor the quarter ended February 28, 2025, and our historical financial statements and notes to those financial statements, in each case that are incorporated by reference in this prospectus supplement and the accompanying prospectus.

|                                                          |     | As of February 28, 2025 |         |     |             |         |
|:---------------------------------------------------------|:----|:------------------------|--------:|:----|:------------|--------:|
|                                                          |     | Actual                  |         |     | As Adjusted |         |
|                                                          |     | -unaudited, in millions |         |     |             |         |
| Cash and cash equivalents                                |     | $                       | 1,563.8 |     | $           | 5,708.9 |
| Debt:                                                    |     |                         |         |     |             |         |
| Revolving credit facilities(1)                           |     |                         |         |     |             |         |
| 2029 credit facility with JPMorgan Chase Bank, N.A.      |     | $                       |       — |     | $           |       — |
|