(a) Every motor carrier subject to the tax hereby imposed shall be entitled to a credit on such tax equivalent to the rate per gallon of the applicable Alabama tax on motor fuel which is currently in effect on all motor fuel purchased by such motor carrier within this state for use in its operations either within or without this state and upon which the motor fuel tax has been paid by such motor carrier. Evidence of the payment of such taxes in such form as may be required by, or is satisfactory to, the commissioner shall be furnished by each such carrier claiming the credit herein allowed. When the amount of the credit herein provided to which any motor carrier is entitled for any quarter exceeds the amount of the tax hereby imposed for which the motor carrier is liable for the same quarter, such excess may under regulations of the commissioner be allowed as a credit on the tax hereby imposed for which such motor carrier would be otherwise liable for any of the three succeeding quarters; or upon application within three years from the end of any quarter, duly verified and presented, in accordance with regulations promulgated by the commissioner and supported by such evidence as may be satisfactory to the commissioner, such excess may be refunded if it shall appear that the applicant has paid to another state under a lawful requirement of such state a tax, similar in effect to the tax herein provided, on the use or consumption in such state of motor fuel purchased in Alabama to the extent of the rate of the rate per gallon of the applicable Alabama tax on motor fuel which is currently in effect.

(b) If the department shall deny a refund in the amount claimed by the applicant, the applicant may appeal such denial pursuant to the provisions provided in Chapter 2A of this title. Whenever any refund is ordered it shall be paid by warrant of the state Comptroller out of the same funds to which disbursed as provided in Section 40-17-146, and there is hereby appropriated out of said funds so much thereof as may be necessary to make refunds from time to time.