business, less a specific deduction under subsection (b)(12), and (C) for purposes of subparagraph (B), unrelated business taxable income with respect to any such trade or business shall not be less than zero. . (b) Effective date (1) In general Except to the extent provided in paragraph (2), the amendment made by this section shall apply to taxable years beginning after December 31, 2017. (2) Carryovers of net operating losses If any net operating loss arising in a taxable year beginning before January 1, 2018, is carried over to a taxable year beginning on or after such date— (A) subparagraph (A) of section 512(a)(6) of the Internal Revenue Code of 1986, as added by this Act, shall not apply to such net operating loss, and (B) the unrelated business taxable income of the organization, after the application of subparagraph (B) of such section, shall be reduced by the amount of such net operating loss. 13704. Repeal of tax-exempt status for professional sports leagues (a) In general Paragraph (6) of section 501(c) is amended— (1) by striking , boards of trade, or professional and all that follows through players) and inserting , or boards of trade , and (2) by adding at the end the following: This paragraph shall not apply to any professional sports league (whether or not administering a pension fund for players). . (b) Effective date The amendments made by this section shall apply to taxable years beginning after December 31, 2017. 13705. Modification of taxes on excess benefit transactions (a) Organization level tax Subsection (a) of section 4958 is amended by adding at the end the following new paragraph: (3) On the organization In any case in which a tax is imposed by paragraph (1), there is hereby imposed on the organization a tax equal to 10 percent of the excess benefit, unless the participation of the organization in the excess benefit transaction is not willful and is due to reasonable cause. . (b) Minimum standards of organization due diligence Subsection (d) of section 4958 is amended by adding at the