26 U.S.C. § 4223

1. (a)For purposes of this chapter, a manufacturer or producer to whom an article is sold or resold free of tax under section 4221(a)(1) for use by him in further manufacture shall be treated as the manufacturer or producer of such article.
2. (b)If the manufacturer or producer referred to in subsection (a) incurs liability for tax under this chapter on his sale or use of an article referred to in subsection (a) and the tax is based on the price for which the article is sold, the article shall be treated as having been sold by him—For purposes of this subsection, the price for which the article was sold shall be determined as provided in section 4216. For purposes of paragraph (2) no adjustment or readjustment shall be made in such price by reason of any discount, rebate, allowance, return or repossession of a container or covering, or otherwise. An election under paragraph (2) shall be made in the return reporting the tax applicable to the sale or use of the article, and may not be revoked.
   1. (1)at the price for which the article was sold by him (or, where the tax is on his use of the article, at the price referred to in section 4218(c)); or
   2. (2)if he so elects and establishes such price to the satisfaction of the Secretary—
      1. (A)at the price for which the article was sold to him; or
      2. (B)at the price for which the article was sold by the person who (without regard to subsection (a)) is the manufacturer, producer, or importer of such article.