For purposes of this subtitle— (1) Taxable carbon substance The term taxable carbon substance means— (A) coal, (B) oil, and (C) natural gas. (2) Coal The term coal includes lignite, anthracite, bituminous, subbituminous, peat or other forms of what is commonly referred to as coal produced from a mine. (3) Oil The term oil includes crude oil condensates, natural gasoline, shale oil, any bitumen or bituminous mixture, any oil derived from a bitumen or bituminous mixture, and any oil derived from kerogen-bearing sources. (4) Natural gas The term natural gas means either natural gas unmixed, or any mixture of natural and artificial gas. (5) Life-cycle emissions The term life-cycle emissions means total life-cycle emissions of carbon dioxide from a taxable carbon substance which shall be determined by the Administrator. (6) Administrator The term Administrator means the Administrator of the Environmental Protection Agency. (7) United States The term United States means the States, and territory or possession of the United States, and the District of Columbia. 9904. Special rules (a) Export For purposes of this subtitle— (1) In general No tax shall be imposed under section 9901 on the production or mining of a taxable carbon substance which is intended for export, including the sale or resale by a purchaser to a second purchaser for export. (2) Proof of export required Rules similar to the rules of section 4221(b) shall apply for purposes of paragraph (1). (3) Credit or refund where tax paid (A) In general Except as provided in subparagraph (B), if— (i) tax under section 9901 was paid with respect to any taxable carbon substance, and (ii) (I) such substance was exported by any person, or (II) such substance was used as a material in the manufacture or production of a substance which was exported by any person and which, at the time of export, was a taxable carbon substance (as defined in section 9902(1)), credit or refund (without interest) of such tax shall be allowed or made to the person who paid such tax. (B)