Does a licensee that engages in both manufacturing and importing need to pay a separate special (occupational) tax for each activity?
Yes. A separate special (occupational) tax payment must be made for each of these activities. However, Class 1 (importer) and Class 2 (manufacturer) special (occupational) taxpayers are qualified to deal in NFA firearms without also having to pay special (occupational) tax as a Class 3 dealer.
[27 CFR 479.39]
Source ATF: https://www.atf.gov/firearms/qa/does-licensee-engages-both-manufacturing-and-importing-need-pay-separate-special