(a) At the time of rendering the statement required by § 5113(a) of this title, the distributor shall pay to the Department of Transportation the tax or taxes levied by this chapter on all gasoline sold and/or used within this State during the preceding calendar month.
(b) Distributors averaging monthly sales and/or use of 500,000 or more gallons over a 12-month period ending April 30 each year shall, when complying with § 5113(b) of this title, pay to the Department of Transportation in June each year the tax or taxes on 75% of the gallons of gasoline estimated to be sold and/or used during said month of June. The balance of the tax due on the actual sales and/or use in June shall be paid on or before the twenty-fifth day of the next calendar month.