SDCL § 10-47B-179: Calculating tax liability of interstate fuel user when user's records are inadequate.

If an interstate fuel user does not keep records adequate to verify either miles traveled or fuel purchased, tax shall be calculated on fuel consumption using the average miles per gallon (AMPG) allowance. The AMPG allowance is either four miles per gallon or a twenty percent reduction of the miles per gallon reported for all miles attributable to established travel. If no records exist to support miles driven during a tax reporting period, the period's mileage shall be calculated based on the average mileage driven during the four preceding reporting periods.