For the purpose of determining the amount of his liability for the tax imposed by this article, each bonded distributor of gasoline shall, not later than the twentieth day of the month next following the month in which this article becomes effective, and not later than the twentieth day of each month thereafter, file with the commission a monthly report which shall include a statement of the number of gallons of gasoline or blend stock received by such distributor within this state during the preceding calendar month, and such other information as may be reasonably necessary for the proper administration of this article.

At the time of filing each monthly report with the commission, a distributor may take a credit for the number of gallons of gasoline that he purchased during the preceding calendar month from a distributor who pays the excise tax imposed by this article on such gasoline.

At the time of filing each monthly report with the commission, each distributor of gasoline shall pay to the commission the full amount of the gasoline tax due from such distributor for the preceding calendar month, less two percent (2%) to cover evaporation, shrinkage and other normal losses.

Reports and payments sent to the commission by mail must be postmarked by the due date in order to be considered timely filed, except when the due date falls on a weekend or holiday, in which case such reports and payments must be postmarked by the first working day following the due date in order to be considered timely filed.

The monthly report of the distributor of gasoline shall be prepared and filed with the commission on forms prescribed by the commission, or the distributor of gasoline may, with the approval of the commission, furnish the required information on machine-prepared schedules. Such monthly reports or schedules shall be signed by the distributor or his duly authorized agent and shall contain a declaration that the statements contained therein are true and correct and are made under the penalty of perjury.