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 title 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. (c) 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. (d) 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.