Iowa Code § 452A.32

The department shall establish a schedule listing the average amount of ethanol contained in E-85 gasoline as defined in section 214A.1, for use by a retail dealer in calculating the retail dealer’s total ethanol gallonage, as provided in section 452A.31. In establishing the schedule, the department shall assume that a retail dealer begins selling and dispensing E-85 gasoline from a motor fuel pump on the first day of a month and ceases selling and distributing E-85 gasoline on the last day of a month.