26 USC 5801 - Imposition of tax

(a) General rule 
On 1st engaging in business and thereafter on or before July 1 of each year, every importer, manufacturer, and dealer in firearms shall pay a special (occupational) tax for each place of business at the following rates:
(1) Importers and manufacturers: $1,000 a year or fraction thereof.
(2) Dealers: $500 a year or fraction thereof.
(b) Reduced rates of tax for small importers and manufacturers 

(1) In general 
Paragraph (1) of subsection (a) shall be applied by substituting $500 for $1,000 with respect to any taxpayer the gross receipts of which (for the most recent taxable year ending before the 1st day of the taxable period to which the tax imposed by subsection (a) relates) are less than $500,000.
(2) Controlled group rules 
All persons treated as 1 taxpayer under section 5061 (e)(3) shall be treated as 1 taxpayer for purposes of paragraph (1).
(3) Certain rules to apply 
For purposes of paragraph (1), rules similar to the rules of subparagraphs (B) and (C) of section 448 (c)(3) shall apply.