Mich. Comp. Laws § 339.730: Contingent fee.

Sec. 730.

Except as otherwise provided in this section, a certified public accountant may charge or receive a contingent fee.

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:

An audit or review of a financial statement.

A compilation of a financial statement when the licensee expects, or may reasonably expect, that a third party will use the financial statement and that the compilation report does not disclose a lack of independence.

An examination of prospective financial information.

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.

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.