Michigan Compiled Laws, Chapter 500. Insurance Code of 1956 § 500.2646

Sec. 2646.  (1) Every member of or subscriber to a rating organization shall adhere to the filings made on its behalf by such organization except that any such insurer may make written application to the commissioner to file a deviation from the class rates, schedules, rating plans or rules respecting any kind of insurance, or class of risk within a kind of insurance, or combination thereof.  Such application shall specify the basis for the modification and a copy shall also be sent simultaneously to such rating organization.  In considering the application to file such deviation the commissioner shall give consideration to the available statistics and the principles for rate making provided in section 2603.  1  The commissioner shall issue an order permitting the deviation for such insurer to be filed if he finds it to be justified and it shall thereupon become effective.  He shall issue an order denying such application if he finds that the deviation applied for does not meet the requirements of this chapter.

(2) Each deviation permitted to be filed shall remain in effect for a period of not less than 1 year from the effective date unless sooner withdrawn by the insurer with the approval of the commissioner or until terminated in accordance with the provisions of sections 2618 or 2620.  2