For the purpose of determining the amount of his liability for the tax imposed by this article, each bonded distributor of special fuel 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 special fuel received and sold by such distributor of special fuel 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 special fuel that he purchased during the preceding calendar month from a distributor who pays the excise tax imposed by this article on such special fuel.

At the time of filing each monthly report with the commission, each distributor of special fuel shall pay to the commission the full amount of the special fuel tax due from such distributor for the preceding calendar month.

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 special fuel shall be prepared and filed with the commission on forms prescribed by the commission, or the distributor of special fuel 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 in such report are true and correct and are made under the penalty of perjury.

When special fuel, which would otherwise be taxable under the provisions of this article, is imported, sold, delivered, or exported, under conditions which will exclude such special fuel from the tax levied under this article by reasons of one or more of the exemptions provided in this article, deduction for such exempt special fuel may be taken without prior approval of the commission on the monthly report of the bonded distributor of special fuel importing, selling, delivering, or exporting such special fuel. Provided, however, that the commission may require proof to be furnished of such deduction for exempt special fuel.

When the Five and Three-fourths Cents (5.75¢) per gallon tax has accrued or has been paid on special fuel that is taxed at Eighteen Cents (18¢) per gallon, a deduction of Five and Three-fourths Cents (5.75¢) per gallon may be made.