Idaho Code § 61-1003
On or before April 1st of each year, each public utility and railroad corporation subject to the jurisdiction of the commission, shall file with the commission a return verified by an officer or agent of the public utility or railroad corporation involved, showing its gross operating revenues from its intrastate utility or railroad business in Idaho for the preceding calendar year during which it carried on such intrastate utility or railroad business. Such return shall be in such form and detail as the commission may prescribe and shall be subject to audit by the commission.
The first return hereunder shall set forth the gross operating revenues derived from intrastate utility or railroad business during the calendar year 1954. The first quarter biennium installment of fees due on the 1955-1956 fiscal appropriation shall be made on or before May 15, 1955, and semiannually thereafter as provided in section 61-1005 of this act.
Idaho Code § 61-1003