The acceptance of any money paid for the excise tax provided for in this article shall in no way preclude the collection of the money actually due; provided, that the money actually paid shall constitute a credit against the money actually due. In the event of the payment of an amount in excess of the amount due, the department may credit such excess against the tax due for any subsequent monthly period, or such excess may be refunded pursuant to the refund procedures in Chapter 2A of this title, provided, that no credit shall be allowed unless made within the time provided for refunds under Chapter 2A of this title.