relating to certain oil spill liability. . (c) Effective date The amendments made by this section shall apply with respect to any liability arising in taxable years ending after the date of the enactment of this Act. 523. Tax on crude oil and natural gas produced from the outer Continental Shelf in the Gulf of Mexico (a) In general Subtitle E of the Internal Revenue Code of 1986 is amended by adding at the end the following new chapter: 56 Tax on severance of crude oil and natural gas from the outer Continental Shelf in the Gulf of Mexico Sec. 5901. Imposition of tax. Sec. 5902. Taxable crude oil or natural gas and removal price. Sec. 5903. Special rules and definitions. 5901. Imposition of tax (a) In general In addition to any other tax imposed under this title, there is hereby imposed a tax equal to 13 percent of the removal price of any taxable crude oil or natural gas removed from the premises during any taxable period. (b) Credit for Federal royalties paid (1) In general There shall be allowed as a credit against the tax imposed by subsection (a) with respect to the production of any taxable crude oil or natural gas an amount equal to the aggregate amount of royalties paid under Federal law with respect to such production. (2) Limitation The aggregate amount of credits allowed under paragraph (1) to any taxpayer for any taxable period shall not exceed the amount of tax imposed by subsection (a) for such taxable period. (c) Tax paid by producer The tax imposed by this section shall be paid by the producer of the taxable crude oil or natural gas. 5902. Taxable crude oil or natural gas and removal price (a) Taxable crude oil or natural gas For purposes of this chapter, the term taxable crude oil or natural gas means crude oil or natural gas which is produced from Federal submerged lands on the outer Continental Shelf in the Gulf of Mexico pursuant to a lease entered into with the United States which authorizes the production. (b) Removal price For purposes of this chapter— (1) In general Except as otherwise