Returns and payment of tax; delinquencies; calculation of fuel used during operations in this state; credit; bond.

(1) The taxes levied under this chapter are due and payable on the first day of the month following the last month of the reporting period. The department may adopt rules for requiring and establishing procedures for annual, semiannual, or quarterly filing. The reporting period is the 12 months beginning January 1 and ending December 31. Each motor carrier licensed or required to be licensed under this chapter must submit a return by the following due dates, except that each due date is extended until the last day of the month of the due date, and, if the last day of the month falls on a Saturday, Sunday, or legal holiday, the due date is further extended until the next day that is not a Saturday, Sunday, or legal holiday:

(a) If annual filing, the due date is January 31;

(b) If semiannual filing, the due dates are January 31 and July 31; or

(c) If quarterly filing, the due dates are January 31, April 30, July 31, and October 31.

(2) The amount of fuel used in the propulsion of any qualified motor vehicle within this state may be calculated, if the motor carrier maintains adequate records, by applying total interstate vehicular consumption of all motor fuel used as related to total miles traveled and applying such rate to total miles traveled within this state. In the absence of adequate documentation by the motor carrier, the department may adopt rules converting miles driven to gallons used.

(3) For the purpose of computing the carrier’s liability for the fuel tax, the total gallons of fuel used in the propulsion of any qualified motor vehicle in this state shall be multiplied by the rates provided in parts I-III of chapter 206. From the sum determined by this calculation, there shall be allowed a credit equal to the amount of the tax per gallon under parts I-III of chapter 206 for each gallon of fuel purchased in this state during the reporting period when the motor fuel tax was paid at the time of purchase. If the tax paid under parts I-III of chapter 206 exceeds the total tax due under this chapter, the excess may be allowed as a credit against future tax payments, until the credit is fully offset or until eight calendar quarters shall have passed since the end of the calendar quarter in which the credit accrued, whichever occurs first. A refund may be made for this credit provided it exceeds $10.

(4) The department may adopt the necessary rules to provide for an adequate bond from each motor carrier to ensure payment of taxes required under this chapter.

(5) Beginning October 1, 2026, except as otherwise authorized by the department, all returns must be submitted electronically through an online system prescribed by the department.