26 CFR 48.4222(a)-1 - Registration.
(a)General rule. Except as provided in § 48.4222(b)-1, tax-free sales under section 4221 may be made only if the manufacturer, first purchaser, and second purchaser, as the case may be, have been registered by the Internal Revenue Service.
(b)Application instructions. Application for registration under section 4222 must be made in accordance with instructions for Form 637 (or such other form as the Commissioner may designate).
(1) For exceptions to the requirement for registration, see section 4222(b) and § 48.4222(b)-1.
(2) For revocation or suspension of registration, see § 48.4222(c)-1.