Idaho Code § 61-305
Under such rules and regulations as the commission may prescribe, every public utility other than a common carrier shall file with the commission within such time and in such form as the commission may designate, and shall print and keep open to public inspection schedules showing all rates, tolls, rentals, charges and classifications collected or enforced, or to be collected or enforced, together with all rules, regulations, contracts, privileges and facilities which in any manner affect or relate to rates, tolls, rentals, classifications or service. The rates, tolls, rentals and charges shown on such schedules when filed by a public utility as to which the commission by this act acquires the power to fix any rates, tolls, rentals or charges, shall not within any portion of the territory as to which the commission acquires as to such public utility such power, exceed the rates, tolls, rentals or charges in effect on the second day of January, 1913, the rates, tolls, rentals and charges shown on such schedules when filed by any public utility as to any territory as to which the commission does not by this act acquire as to such public utility such power, shall not exceed the rates, tolls, rentals and charges in effect at the time the commission acquires as to such territory and as to such public utility, the power to fix rates, tolls, rentals or charges. Nothing in this section contained shall prevent the commission from approving or fixing the rates, tolls, rentals or charges, from time to time, in excess or less than those shown by said schedules.
Idaho Code § 61-305