26 U.S.C. § 4083

(a) Taxable fuel For purposes of this subpart— (1) In general The term “taxable fuel” means— (A) gasoline, (B) diesel fuel, and (C) kerosene. (2) Gasoline The term “gasoline”— (A) includes any gasoline blend, other than qualified methanol or ethanol fuel (as defined in section 4041(b)(2)(B)), partially exempt methanol or ethanol fuel (as defined in section 4041(m)(2)), or a denatured alcohol, and (B) includes, to the extent prescribed in regulations— (i) any gasoline blend stock, and (ii) any product commonly used as an additive in gasoline (other than alcohol). For purposes of subparagraph (B)(i), the term “gasoline blend stock” means any petroleum product component of gasoline. (3) Diesel fuel (A) In general The term “diesel fuel” means— (i) any liquid (other than gasoline) which is suitable for use as a fuel in a diesel-powered highway vehicle, or a diesel-powered train, (ii) transmix, and (iii) diesel fuel blend stocks identified by the Secretary. (B) Transmix For purposes of subparagraph (A), the term “transmix” means a byproduct of refined products pipeline operations created by the mixing of different specification products during pipeline transportation. (b) Commercial aviation For purposes of this subpart, the term “commercial aviation” means any use of an aircraft in a business of transporting persons or property for compensation or hire by air, unless properly allocable to any transportation exempt from the taxes imposed by sections 4261 and 4271 by reason of section 4281 or 4282 or by reason of subsection (h) or (i) of section 4261. Such term shall not include the use of any aircraft before October 1, 2028 , if tax is imposed under section 4043 with respect to the fuel consumed in such use or if no tax is imposed on such use under section 4043 by reason of subsection (c)(5) thereof. (c) Certain uses defined as removal If any person uses taxable fuel (other than in the production of taxable fuels or special fuels referred to in section 4041), such use shall for the purposes of this chapter be considered a removal. (d) Administrative authority (1) In general In addition to the authority otherwise granted by this title, the Secretary may in administering compliance with this subpart, section 4041, and penalties and other administrative provisions related thereto— (A) enter any place at which taxable fuel is produced or is stored (or may be stored) for purposes of— (i) examining the equipment used to determine the amount or composition of such fuel and the equipment used to store such fuel, (ii) taking and removing samples of such fuel, and (iii) inspecting any books and records and any shipping papers pertaining to such fuel, and (B) detain, for the purposes referred in subparagraph (A), any container which contains or may contain any taxable fuel. (2) Inspection sites The Secretary may establish inspection sites for purposes of carrying out the Secretary’s authority under paragraph (1)(B). (3) Penalty for refusal of entry (A) Forfeiture The penalty provided by section 7342 shall apply to any refusal to admit entry or other refusal to permit an action by the Secretary authorized by paragraph (1), except that section 7342 shall be applied by substituting “$1,000” for “$500” for each such refusal. (B) Assessable penalty For additional assessable penalty for the refusal to admit entry or other refusal to permit an action by the Secretary authorized by paragraph (1), see section 6717.