How does a person qualify to import, manufacture, or deal in NFA firearms?
The person must be licensed under the GCA and pay the required special (occupational) tax imposed by the NFA. After becoming licensed under the GCA, the licensee must file an ATF Form 5630.7, Special Tax Registration and Return National Firearms Act (NFA) with the appropriate tax payment with ATF. In addition, an importer (except importers of sporting shotguns and shotgun ammunition) must also be registered with ATF under the Arms Export Control Act of 1976, by filing an ATF Form 4587, Application to Register as an Importer of U.S. Munitions Import List Articles.
[26 U.S.C. 5801; 18 U.S.C. 923; 27 CFR 447.31, 478.41 and 479.34]
Source ATF: https://www.atf.gov/firearms/qa/how-does-person-qualify-import-manufacture-or-deal-nfa-firearms