by the Secretary of the Treasury as being equal to the aggregate benefits (if any) that would have been provided to residents of such possession by reason of the provisions of this section (other than this subsection) with respect to section 32 of the Internal Revenue Code of 1986 if a mirror code tax system had been in effect in such possession. The preceding sentence shall not apply unless the respective possession has a plan, which has been approved by the Secretary of the Treasury, under which such possession will promptly distribute such payments to its residents. (3) Mirror code tax system For purposes of this section, 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. (4) Treatment of payments For purposes of section 1324 of title 31, United States Code, the payments under this section shall be treated in the same manner as a refund due from a credit provision referred to in subsection (b)(2) of such section. D Child tax credit 20131. Child tax credit improvements for 2020 (a) In general Section 24 of the Internal Revenue Code of 1986 is amended by adding at the end the following new subsection: (i) Special rules for 2020 In the case of any taxable year beginning in 2020— (1) Refundable credit Subsection (h)(5) shall not apply and the increase determined under the first sentence of subsection (d)(1) shall be the amount determined under subsection (d)(1)(A) (determined without regard to subsection (h)(4)). (2) Credit amount Subsection (h)(2) shall not apply and subsection (a) shall be applied by substituting $3,000 ($3,600 in the case of a qualifying child who has not attained age 6 as of the close of the calendar year in which the taxable year of the taxpayer begins) for $1,000 . (3) 17-year-olds eligible for treatment as