Idaho Code § 61-1005
On or before May 1st of each year, the commission shall notify each public utility and railroad corporation subject to the provisions of this act, by mail, of the amount of its fee for the ensuing fiscal year beginning July 1st, computed as in this act provided. Such fee shall be paid to the commission in equal semiannual installments on or before the 15th days of November and May in each fiscal year. If payment shall not be made on or before said respective dates, the installments so due shall bear interest at the rate of six per cent (6%) per annum until such time as the full amount of the installment shall have been paid. Upon failure, refusal or neglect of any public utility or railroad corporation to pay such fee the attorney general shall commence an action in the name of the state to collect the same.
Idaho Code § 61-1005