When a supplier or distributor in motor vehicle fuels makes a sale to a retail outlet, the supplier or distributor shall credit the retail outlet with one-half of one percent of the total state motor vehicle fuel tax applied to the gallonage sold. This must appear on the face of the delivery invoice at the time of delivery of the motor vehicle fuel in consideration of evaporation and shrinkage losses and the retail outlet’s cost of collection of the tax. On making payments to the commissioner as provided in this chapter, the supplier or distributor shall deduct the total credit allowance granted on sales to retail outlets in motor vehicle fuels under the provisions of this section, in addition to other deductions allowed, from the amount of tax due.