Act ( 42 U.S.C. 300gg(a)(1)(A)(iii) ) is amended by inserting after (consistent with section 2707(c)) the following: or, for plan years beginning on or after January 1, 2021, as the Secretary may implement through interim final regulation, 5 to 1 for adults (consistent with section 2707(c)) . 226. Premium assistance adjustment to reflect age (a) Modification of applicable percentage Section 36B(b)(3)(A) of the Internal Revenue Code of 1986 is amended to read as follows: (A) Applicable percentage (i) In general The applicable percentage for any taxable year shall be the percentage such that the applicable percentage for any taxpayer whose household income is within an income tier specified in the following table shall increase, on a sliding scale in a linear manner, from the initial percentage to the final percentage specified in such table for such income tier with respect to a taxpayer of the age involved: In the case of household income (expressed as a percent of the poverty line) within the following income tier: Up to Age 29 Age 30–39 Age 40–49 Age 50–59 Over Age 59 Initial % Final % Initial % Final % Initial % Final % Initial % Final % Initial % Final % Up to 100% 0 0 0 0 0 0 0 0 0 0 100%–133% 2 2 2 2 2 2 2 2 2 2 133%–150% 3 4.3 3 4.3 3 4.3 3 4.3 3 4.3 150%–200% 4.3 6.7 4.3 6.7 4.3 6.7 4.3 6.7 4.3 6.7 200%–250% 6.7 6.7 6.7 7.6 6.7 8.5 6.7 8.5 6.7 8.5 250%–300% 6.7 6.7 7.6 7.6 8.3 9.8 8.3 9.8 8.3 9.8 300%–400% 6.7 7 7.6 8 9.8 10 9.8 10 9.8 10 400%-600% 7 9 8 10 10 15 10 15 10 15 (ii) Age determinations (I) In general For purposes of clause (i), the age of the taxpayer taken into account under clause (i) with respect to any taxable year is the age attained by such taxpayer before the close of such taxable year. (II) Joint returns In the case of a joint return, the age of the older spouse shall be taken into account under clause (i). (iii) Indexing In the case of any taxable year beginning after calendar year 2021, the initial and final percentages contained in clause (i) shall be adjusted to reflect— (I) the