Mich. Comp. Laws § 600.1910

Sec. 1910. (1) Proof of service of process must be made by 1 of the following methods: (a) Written acknowledgment of the receipt of a summons and a copy of the complaint, dated and signed by the person authorized under this act to receive them. (b) A certificate, stating the facts of service, if service is made in this state by any of the following: (i) A sheriff. (ii) A deputy sheriff, medical examiner, court officer, or constable, or a deputy of any of these officers. (c) If service is made by any other individual, a written statement of the facts of service that is signed and dated and verified by the following statement: "I declare under the penalty of perjury that this proof of service has been examined by me and that its contents are true to the best of my information, knowledge, and belief.". (2) Failure to make proof of service does not affect the validity of the service.