No business license tax or any portion thereof shall be refundable except in the case of an error in the determination of the amount of the license tax or in the event of double payment for a license. Claims for refunds based on the foregoing reasons must be made within three years of the discovery of such error in calculation or overpayment and shall be accompanied by documentation proving overpayment as required by the director. (Ord. 635; Ord. 473 §1, 2002).