Opinion of the Court
compensating for personal injuries; railroads pay the full excise tax on such compensation; and employees receive full credit for the compensation in determining their retirement benefits. That scheme, however, is not plausibly attributable to Congress.
For federal income tax purposes, “gross income” means “all income” “[e]xcept as otherwise provided.” 26 U. S. C. §61; see §§1, 63 (imposing a tax on “taxable income,” defined as “gross income minus… deductions”). Congress provided detailed prescriptions on the scope of “gross income,” excluding from its reach numerous items, among them, personal injury damages. See §§101–140. Conspicuously absent from the RRTA, however, is any reference to “gross income.” As employed in the RRTA, the word “income” merely distinguishes the tax on the employee, an “income… tax,” §3201, from the matching tax on the railroad, called an “excise tax.” §§3201, 3221. See also 1937 RRTA, §§2–3 (establishing an “income tax on employees” and an “excise tax on employers”); S. Rep. No. 818, 75th Cong., 1st Sess., 5 (1937) (stating that the RRTA imposes an “income tax on employees” and an “excise tax on employers”); H. R. Rep. No. 1071, 75th Cong., 1st Sess., 6 (1937) (same).
Congress, we reiterate, specified not “gross income” but employee “compensation” as the tax base for the RRTA’s income and excise taxes. §§3201, 3221. Congress then excepted certain payments from the calculation of “compensation.” See §3231(e); supra, at 9. Congress adopted by cross-reference particular Internal Revenue Code exclusions from “gross income,” thereby carving out those specified items from RRTA coverage. See §3231(e)(5)–(6), (9)–(11). Tellingly, Congress did not adopt for RRTA purposes the exclusion of personal injury damages from federal income taxation set out in §104(a)(2). We note, furthermore, that if RRTA taxes were based on “income” or “gross income” rather than “compensation,” the RRTA
