; or (2) impact the Federal Hospital Insurance Trust Fund under section 1817 or the Federal Supplementary Medical Insurance Trust Fund under section 1841 (including the Medicare Prescription Drug Account within such Trust Fund). . 3. Reinsurance (a) In general The Secretary of Health and Human Services shall establish a mechanism to pool, on a nationwide basis, the costs of the highest-cost patients enrolled in individual health insurance coverage (as defined in section 2791 of the Public Health Service Act ( 42 U.S.C. 300gg–91 )) offered on or off the Exchanges, to the extent such costs are not already pooled pursuant to section 1343 of the Patient Protection and Affordable Care Act ( 42 U.S.C. 18063 ), for the purpose of reducing premiums for such individual health insurance coverage. (b) Authorization of appropriations For purposes of carrying out paragraph (1), there is authorized to be appropriated $10,000,000,000 for each of fiscal years 2021, 2022, and 2023. 4. Expansion of tax credit (a) In general Subparagraph (A) of section 36B(c)(1) of the Internal Revenue Code of 1986 is amended by striking but does not exceed 400 percent . (b) Applicable percentages Clause (i) of section 36B(b)(3)(A) of the Internal Revenue Code of 1986 is amended to read as follows: (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 premium percentage to the final premium percentage specified in such table for such income tier: In the case of household income (expressed as a percent of poverty line) within the following income tier: The initial premium percentage is— The final premium percentage is— Up to 138 percent 1.5 1.5 138 percent up to 150 percent 2.5 3.5 150 percent up to 200 percent 3.5 5.8 200 percent up to 250 percent 5.8 7.55 250 percent up to 300 percent 7.55 9.0 300 percent up to