Mich. Admin. Code R. 421.302
Rule 302. When an employer is entitled to designate, pursuant to section 48 of the Michigan employment security act, vacation pay to a period of layoff, forced vacation, or other separation, the employer shall either deliver to the affected employee and to the employee's bargaining representative, if any, on or before the employee's last day of work, written notice of such designation stating that such designation may render the employee ineligible for unemployment benefits during the designated period or shall post such notice conspicuously in easily accessible places frequented by employees and deliver a copy thereof to the employee's bargaining representative, if any. However, as to an individual laid off prior to the time of designation, posting of the notice shall not substitute for the requirement of delivery of the notice to such individual by mail.
Mich. Admin. Code R. 421.302