Michigan Compiled Laws, Chapter 339. Occupational Code § 339.730

Sec. 730.  (1) Except as otherwise provided in this section, a certified public accountant may charge or receive a contingent fee.

(2) A licensee shall not charge or receive a contingent fee from a client during the period in which a licensee or a licensee's firm is engaged to perform for the client 1 or more of the following services or during the period of time covered by any of such client's historical financial statements involved in those services:

(3) A licensee shall not charge or receive a contingent fee for the preparation of an original or amended tax return or claim for a tax refund.

(4) As used in this section, “contingent fee” means a fee established for the performance of a service pursuant to an arrangement in which no fee will be charged unless a specified finding or result is attained or in an arrangement where the amount of the fee is dependent upon a finding or result of the service.  Contingent fee does not include a fee fixed by a court or other public authority and, in tax matters, a fee determined based upon the results of judicial proceedings or the findings of a governmental agency.