subsection, the term possession of the United States shall include such possessions as are specified in section 937(a)(1) of the Internal Revenue Code of 1986. (B) Mirror code tax system For purposes of this subsection, the term mirror code tax system means, with respect to any possession of the United States, the income tax system of such possession if the income tax liability of the residents of such possession under such system is determined by reference to the income tax laws of the United States as if such possession were the United States, and such system includes a tax credit substantially identical to the credit allowed under this section. (C) Treatment of payments For purposes of section 1324(b)(2) of title 31, United States Code, or any similar rule of law, any payment made under this subsection shall be treated in the same manner as a refund due from the credit allowed under this section. . (b) Effective date The amendment made by this section shall apply with respect to taxable years beginning after December 31, 2018.