26 U.S.C. § 4051

1. (a)
   1. (1)There is hereby imposed on the first retail sale of the following articles (including in each case parts or accessories sold on or in connection therewith or with the sale thereof) a tax of 12 percent of the amount for which the article is so sold:
      1. (A)Automobile truck chassis.
      2. (B)Automobile truck bodies.
      3. (C)Truck trailer and semitrailer chassis.
      4. (D)Truck trailer and semitrailer bodies.
      5. (E)Tractors of the kind chiefly used for highway transportation in combination with a trailer or semitrailer.
   2. (2)The tax imposed by paragraph (1) shall not apply to automobile truck chassis and automobile truck bodies, suitable for use with a vehicle which has a gross vehicle weight of 33,000 pounds or less (as determined under regulations prescribed by the Secretary).
   3. (3)The tax imposed by paragraph (1) shall not apply to truck trailer and semitrailer chassis and bodies, suitable for use with a trailer or semitrailer which has a gross vehicle weight of 26,000 pounds or less (as determined under regulations prescribed by the Secretary).
   4. (4)The tax imposed by paragraph (1) shall not apply to tractors of the kind chiefly used for highway transportation in combination with a trailer or semitrailer if—
      1. (A)such tractor has a gross vehicle weight of 19,500 pounds or less (as determined by the Secretary), and
      2. (B)such tractor, in combination with a trailer or semitrailer, has a gross combined weight of 33,000 pounds or less (as determined by the Secretary).
   5. (5)For purposes of this subsection, a sale of an automobile truck or truck trailer or semitrailer shall be considered to be a sale of a chassis and of a body described in paragraph (1).
2. (b)Under regulations prescribed by the Secretary—
   1. (1)If—then there is hereby imposed on such installation a tax equal to 12 percent of the price of such part or accessory and its installation.
      1. (A)the owner, lessee, or operator of any vehicle which contains an article taxable under subsection (a) installs (or causes to be installed) any part or accessory on such vehicle, and
      2. (B)such installation is not later than the date 6 months after the date such vehicle (as it contains such article) was first placed in service,
   2. (2)Paragraph (1) shall not apply if—
      1. (A)the part or accessory installed is a replacement part or accessory, or
      2. (B)the aggregate price of the parts and accessories (and their installation) described in paragraph (1) with respect to any vehicle does not exceed $1,000 (or such other amount or amounts as the Secretary may by regulations prescribe).
   3. (3)The owners of the trade or business installing the parts or accessories shall be secondarily liable for the tax imposed by paragraph (1).
3. (c)On and after October 1, 2028, the taxes imposed by this section shall not apply.
4. (d)If—there shall be allowed as a credit against the tax imposed by this subchapter an amount equal to the tax (if any) imposed by section 4071 on such tires.
   1. (1)tires are sold on or in connection with the sale of any article, and
   2. (2)tax is imposed by this subchapter on the sale of such tires,