Michigan Proof of Mailing is a service offered by the Michigan Department of Treasury that provides evidence that a document was sent by mail. It includes an official postmark, date, and a unique tracking number. Michigan Proof of Mailing offers two types of services: Express Mailing and Standard Mailing. Express Mailing is a same-day service that provides same-day postmarking and delivery confirmation. Standard Mailing is a service that provides next-day postmarking and tracking information. Both services include a unique tracking number, along with a postmark that includes the date, time, and location of mailing. This service is used to provide evidence that documents were sent in a timely manner.