Mich. Comp. Laws § 257.1334

Sec. 34. A motor vehicle repair facility, including a gasoline service station which performs any of the repairs listed in the repair categories of certification for specialty mechanics or developed by the administrator by rule, shall give to each customer a written statement upon return of the repaired vehicle to the customer. The statement shall disclose: (a) Repairs needed, as determined by the facility. (b) Repairs requested by the customer. (c) Repairs authorized by the customer. (d) The facility's estimate of repair costs. (e) The actual cost of repairs. (f) The repairs or services performed, including a detailed identification of all parts that were replaced and a specification as to which are new, used, rebuilt, or reconditioned. (g) A certification that the repairs were completed properly or a detailed explanation of an inability to complete repairs properly. The statement shall be signed by the owner of the facility or by a person designated by the owner to represent the facility. The name of the mechanic or mechanics who performed the diagnosis and the repair shall also appear on the statement.