If it shall appear that an amount of tax has been paid which was not due under the provisions of this subchapter, whether as the result of a mistake of fact or error of law, then the amount shall be credited against any tax due, or to become due, under this subchapter from the taxpayer who made the erroneous payment; provided, that no amounts paid in error more than three years prior to the filing of a claim therefor shall be so credited.
(`70 Code, § 20-27) (Ord. 321, passed 10-13-81)