26 USC 5051 - Imposition and rate of tax

(a) Rate of tax 

(1) In general 
A tax is hereby imposed on all beer brewed or produced, and removed for consumption or sale, within the United States, or imported into the United States. Except as provided in paragraph (2), the rate of such tax shall be $18 for every barrel containing not more than 31 gallons and at a like rate for any other quantity or for fractional parts of a barrel.
(2) Reduced rate for certain domestic production 

(A) $7 a barrel rate 
In the case of a brewer who produces not more than 2,000,000 barrels of beer during the calendar year, the per barrel rate of the tax imposed by this section shall be $7 on the first 60,000 barrels of beer which are removed in such year for consumption or sale and which have been brewed or produced by such brewer at qualified breweries in the United States.
(B) Controlled groups 
In the case of a controlled group, the 2,000,000 barrel quantity specified in subparagraph (A) shall be applied to the controlled group, and the 60,000 barrel quantity specified in subparagraph (A) shall be apportioned among the brewers who are component members of such group in such manner as the Secretary or his delegate shall by regulations prescribed. For purposes of the preceding sentence, the term controlled group has the meaning assigned to it by subsection (a) of section 1563, except that for such purposes the phrase more than 50 percent shall be substituted for the phrase at least 80 percent in each place it appears in such subsection. Under regulations prescribed by the Secretary or his delegate, principles similar to the principles of the preceding two sentences shall be applied to a group of brewers under common control where one or more of the brewers is not a corporation.
(C) Regulations 
The Secretary may prescribe such regulations as may be necessary to prevent the reduced rates provided in this paragraph from benefiting any person who produces more than 2,000,000 barrels of beer during a calendar year.
(3) Tolerances 
Where the Secretary or his delegate finds that the revenue will not be endangered thereby, he may by regulations prescribe tolerances for barrels and fractional parts of barrels, and, if such tolerances are prescribed, no assessment shall be made and no tax shall be collected for any excess in any case where the contents of a barrel or a fractional part of a barrel are within the limit of the applicable tolerance prescribed.
(b) Assessment on materials used in production in case of fraud 
Nothing contained in this subpart or subchapter G shall be construed to authorize an assessment on the quantity of materials used in producing or purchased for the purpose of producing beer, nor shall the quantity of materials so used or purchased be evidence, for the purpose of taxation, of the quantity of beer produced; but the tax on all beer shall be paid as provided in section 5054, and not otherwise; except that this subsection shall not apply to cases of fraud, and nothing in this subsection shall have the effect to change the rules of law respecting evidence in any prosecution or suit.
(c) Illegally produced beer 
The production of any beer at any place in the United States shall be subject to tax at the rate prescribed in subsection (a) and such tax shall be due and payable as provided in section 5054 (a)(3) unless
(1) such beer is produced in a brewery qualified under the provisions of subchapter G, or
(2) such production is exempt from tax under section 5053 (e) (relating to beer for personal or family use).