Ala. Code § 40-2-8

The Commissioner of the Department of Revenue, the secretary of the department and all stenographers, experts, engineers, and assistants who may be employed by the department shall be entitled to receive their actual expenses while traveling or acting on the business of the department, such expenses to be itemized and sworn to by the person who incurs the same, and vouchers attached as now provided by law, and shall be approved by said department and also by the Governor, such expenses not to exceed any maximum fixed by law. Such expenses shall be paid by the Treasurer out of the appropriation made for the annual expenses of the Department of Revenue or out of the fund or funds out of which such expenses are properly payable upon warrant drawn by the Comptroller upon such fund or funds.