27 CFR 70.125 - Abatements.
(a) The appropriate TTB officer may abate the unpaid portion of any assessment or liability, if the assessment is in excess of the correct tax liability, if the assessment is made subsequent to the expiration of the period of limitation applicable thereto, or if the assessment has been erroneously or illegally made.
(b) If more than the correct amount of tax, interest, additional amount, addition to the tax, or assessable penalty is assessed but not paid to TTB, the person against whom the assessment is made may file a claim for abatement of such overassessment. Each claim for abatement under this section shall be made on Form 2635 (5020.8), Claim - Alcohol, Tobacco and Firearms Taxes, in accordance with the instructions on the form. All such claims must be filed with the appropriate TTB officer who made demand for the amount assessed.
(c) The appropriate TTB officer may issue uniform instructions to abate amounts the collection of which is not warranted because of the administration and collection costs.