Mich. Comp. Laws § 41.350k

Sec. 20k. After the creation of a special assessment district authorized by section 20b and while bonds are still outstanding, the township board may annually determine the amount to be assessed in the district and then levy that amount of annual assessments as special assessments against the benefited properties within the district. Further hearings shall not be held unless a change in the amount of annual assessment against an individual property is contemplated or attempted.