EXHIBIT 23 Consent of Independent Registered Public Accounting Firm
We consent to the incorporation by reference in the Registration Statement (Form S-8 No.
333-84055) pertaining to the Paychex, Inc. 401(k) Incentive Retirement Plan of our report dated May
25, 2006, with respect to the financial statements and schedules of Paychex, Inc. 401(k) Incentive
Retirement Plan included in this Annual Report (Form 11-K) for the year ended December 31, 2005.
/s/ Ernst & Young LLP
June 19, 2006
Cleveland, Ohio
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