Any person, firm, or corporation taxable under this part having a cash and credit business may report such cash business, and the taxpayer shall thereafter include in each monthly report all credit collections made during the month preceding and shall pay the taxes due thereon at the time of filing such report, but in no event shall the gross proceeds of such credit business be included in the measure of the tax to be paid until collections of such credit business shall have been made.
Ala. Code § 45-3A-51.03 (1975)