((a)) ** Business with United States** Any person required to pay special (occupational) tax under section 5801 shall be relieved from payment of that tax if he establishes to the satisfaction of the Secretary that his business is conducted exclusively with, or on behalf of, the United States or any department, independent establishment, or agency thereof. The Secretary may relieve any person manufacturing firearms for, or on behalf of, the United States from compliance with any provision of this chapter in the conduct of such business.

((b)) ** Application** The exemption provided for in subsection (a) of this section may be obtained by filing with the Secretary an application on such form and containing such information as may by regulations be prescribed. The exemptions must thereafter be renewed on or before July 1 of each year. Approval of the application by the Secretary shall entitle the applicant to the exemptions stated on the approved application.