If it shall appear that an amount of tax has been paid that was not due under the provisions of this article, whether as the result of a mistake of fact or an error of law, then such amount shall be credited against any tax due or to become due under this article from the retailer who made the erroneous payment and, if necessary, the retailer shall make the necessary arrangements to refund or credit the taxpayer who paid an erroneous tax to the retailer; provided, that no amounts erroneously paid more than three years prior to the filing of a claim therefor shall be so credited.