Michigan Compiled Laws, Chapter 460. Public Utilities § 460.57

Sec. 7. Any corporation, joint stock company, association, or individual operating a public utility within this state subject to the provisions of this act shall have and maintain a principal office within this state. All books, accounts, papers, and records pertaining to the business and operation of the utility shall be kept in the office, unless the commission by special order or by rule or regulation may otherwise provide. Schedules of rates in a form and in such detail as the commission may direct shall be filed in the office of the commission and copies of the schedules shall be printed and posted in the principal office of the utility and other such locations as the commission may direct. A schedule shall not be operative unless and until it has been approved by the commission; nor shall any change be made in the schedules except upon approval of the commission. The commission may adopt rules and regulations governing the presentation of the schedules and desired changes, and action on the schedules, and shall have full authority to regulate the procedure to be observed.