for such calendar year. (c) Definitions For purposes of this subchapter— (1) Specified social security tax The term specified social security tax means— (A) the tax imposed by section 3101(a) (and so much of the tax imposed by section 3201(a) or section 3211(a) as is determined by reference to the tax imposed by section 3101(a)), and (B) 1/2 the tax imposed by section 1401(a). (2) Social security trust fund The term social security trust fund means— (A) the Federal Old-Age and Survivors Insurance Trust Fund established by section 201(a) of the Social Security Act, (B) the Federal Disability Insurance Trust Fund established by section 201(b) of the Social Security Act, and (C) the Social Security Equivalent Benefit Account established under section 15A of the Railroad Retirement Act of 1974. (d) Determination based on estimates Determinations under this section and sections 2 and 3 of the Raise Wages, Cut Carbon Act of 2019 shall be made on the basis of estimates by the Secretary. To the extent that any such determination for any period is determined to have been inaccurate, such determination for the subsequent period shall be appropriately increased or decreased by the amount that the previous determination was less than, or in excess of, the more accurate determination. (e) Publication of rate reductions Any adjustment under this section of social security tax rates for any calendar year shall be published in the Federal Register not later than 2 months before the beginning of such calendar year. II Tax on combustible fossil fuels Sec. 4692. Imposition of tax. Sec. 4693. Refunds or credits. Sec. 4694. Other definitions and special rules. 4692. Imposition of tax (a) In general There is hereby imposed a tax on any taxable carbon substance sold by the manufacturer, producer, or importer thereof. (b) Amount of tax (1) In general The amount of tax imposed by subsection (a) on any taxable carbon substance shall be the applicable amount per ton of the carbon dioxide emissions potential of such substance, as