Ala. Code § 40-12-268

The registration fee or license tax herein required to be paid on motor vehicles shall be in lieu of all other privilege or license taxes which the state or any county or municipality thereof might impose, where the motor vehicle is used by the owner; provided, that only one such license tax can be levied and collected on one and the same motor vehicle for one and the same period of time; provided further, that incorporated cities and towns are hereby authorized to collect a reasonable license or privilege tax on motor vehicles used for carrying passengers or freight for hire.