(a) General. The appropriate TTB officer may credit the tax (including additions thereto) paid for an incorrect stamp if the taxpayer has filed an amended return showing the correct tax on TTB Form 5630.5t and has, with the amended return, surrendered the incorrect stamp for credit.

(b) Underpayment. Where the correct tax (including any additions thereto) exceeds the incorrect tax paid, the appropriate TTB officer may credit the tax paid against the correct tax upon remittance of the difference between the tax paid and the correct tax plus any additions thereto.

(c) Overpayment. Where the tax (and additions thereto) paid for the surrendered incorrect stamp exceeds the amount due, the appropriate TTB officer will advise the taxpayer to file a claim for refund of that excess on TTB Form 5620.8. Sections 46.136 through 46.138 apply to all claims for refund.