Michigan Compiled Laws, Chapter 460. Public Utilities § 460.112

Sec. 2. The department within 30 days after the enactment into law of any appropriation to it, shall ascertain the amount of the appropriation attributable to the regulation of public utilities. This amount shall be assessed against the public utilities and shall be apportioned amongst them as follows: The gross revenue for the preceding calendar year derived from intrastate operations for each public utility shall be totaled and each public utility shall pay a portion of the assessment in the same proportion that its gross revenue for the preceding calendar year derived from intrastate operations bears to such total. Each public utility shall pay a minimum assessment of not less than $50.00.