If it shall appear that an amount of tax has been paid which was not due under the provisions of this chapter, whether as the result of a mistake of fact or

an error of law, then such amount shall be credited against the tax due, or to become due, under this chapter from the taxpayer who made the erroneous payment; provided that, however, no amounts erroneously paid more than three years prior to the filing of a claim therefor shall be so credited. (Ord. 472 § 7, 1981)