Mich. Comp. Laws § 141.685

Sec. 85. (1) After the hearing or informal conference as provided in section 84, the administrator or the department shall issue a final assessment setting forth the total amount found due in the proposed assessment or notice of intent to assess and any adjustment he or she may have made as a result of the protest. The final assessment shall be served in the same manner as a proposed assessment or notice of intent to assess. Proof of mailing of the final assessment is prima facie evidence of receipt of the final assessment by the addressee. (2) If a protest under section 84 is not filed in respect to a proposed assessment or notice of intent to assess, a taxpayer or employer is considered to have received a final assessment 30 days after receipt of the proposed assessment or 60 days after receipt of the notice of intent to assess.