All applications for refund based upon exportations of motor vehicle fuel from this State shall be filed with the Nevada Tax Commission within three (3) months from the date of exportation. All other applications, together with the necessary supporting evidence, shall be filed with the Tax Commission within six (6) months from the date of purchase. All rights to refunds shall be forfeited if applications are not filed with the Tax Commission within the times herein prescribed. (Ord. 60 Art. VII(F), 1976)