Ala. Code § 40-17-165

If an out-of-state vehicle comes to a propane dealer or supplier in the State of Alabama to purchase fuel, the dealer must collect in lieu of any fees levied by this chapter an amount equal to the current Alabama motor fuel tax in effect as prescribed by subdivision (a)(2) of Section 40-17-325, and remit these funds to the Alabama LP-Gas Board before the 20th of the following month after the date of the sale. Decals for out-of-state vehicles can be purchased with decal fees and issuance fees to be paid as prescribed by Sections 40-17-160 and 40-17-161.