26 C.F.R. § 1.1-1
Income tax on individuals
(a) General rule. (1) Section 1 of the Code imposes an income tax on the income of every individual who is a citizen or resident of the United States and, to the extent provided by section 871(b) or 877(b), on the income of a nonresident alien individual. For optional tax in the case of taxpayers with adjusted gross income of less than $10,000 (less than $5,000 for taxable years beginning before January 1, 1970) see section 3. The tax imposed is upon taxable income (determined by subtracting the allowable deductions from gross income). The tax is determined in accordance with the table contained in section 1. See subparagraph (2) of this paragraph for reference guides to the appropriate table for taxable years beginning on or after January 1, 1964, and before January 1, 1965, taxable years beginning after December 31, 1964, and before January 1, 1971, and taxable years beginning after December 31, 1970. In certain cases credits are allowed against the amount of the tax. See part IV (section 31 and following), subchapter A, chapter 1 of the Code. In general, the tax is payable upon the basis of returns rendered by persons liable therefor (subchapter A (sections 6001 and following), chapter 61 of the Code) or at the source of the income by withholding. For the computation of tax in the case of a joint return of a husband and wife, or a return of a surviving spouse, for taxable years beginning before January 1, 1971, see section 2. The computation of tax in such a case for taxable years beginning after December 31, 1970, is determined in accordance with the table contained in section 1(a) as amended by the Tax Reform Act of 1969. For other rates of tax on individuals, see section 5(a). For the imposition of an additional tax for the calendar years 1968, 1969, and 1970, see section 51(a).
(2)(i) For taxable years beginning on or after January 1, 1964, the tax imposed upon a single individual, a head of a household, a married individual filing a separate return, and estates and trusts is the tax imposed by section 1 determined in accordance with the appropriate table contained in the following subsection of section 1:
| Taxable years beginning in 1964 | Taxable years beginning after 1964 but before 1971 | Taxable years beginning after Dec. 31, 1970 (references in this column are to the Code as amended by the Tax Reform Act of 1969) | |
|---|---|---|---|
| Single individual | Sec. 1(a)(1) | Sec. 1(a)(2) | Sec. 1(c). |
| Head of a household | Sec. 1(b)(1) | Sec. 1(b)(2) | Sec. 1(b). |
| Married individual filing a separate return | Sec. 1(a)(1) | Sec. 1(a)(2) | Sec. 1(d). |
| Estates and trusts | Sec. 1(a)(1) | Sec. 1(a)(2) | Sec. 1(d). |
(ii) For taxable years beginning after December 31, 1970, the tax imposed by section 1(d), as amended by the Tax Reform Act of 1969, shall apply to the income effectively connected with the conduct of a trade or business in the United States by a married alien individual who is a nonresident of the United States for all or part of the taxable year or by a foreign estate or trust. For such years the tax imposed by section 1(c), as amended by such Act, shall apply to the income effectively connected with the conduct of a trade or business in the United States by an unmarried alien individual (other than a surviving spouse) who is a nonresident of the United States for all or part of the taxable year. See paragraph (b)(2) of § 1.871-8.
(3) The income tax imposed by section 1 upon any amount of taxable income is computed by adding to the income tax for the bracket in which that amount falls in the appropriate table in section 1 the income tax upon the excess of that amount over the bottom of the bracket at the rate indicated in such table.
(4) The provisions of section 1 of the Code, as amended by the Tax Reform Act of 1969, and of this paragraph may be illustrated by the following examples:
| Tax on $14,000 (from table) | $3,790.00 |
| Tax on $1,750 (at 41 percent as determined from the table) | 717.50 |
| Total tax on $15,750 | 4,507.50 |
| Tax on $14,000 (from table) | $3,550.00 |
| Tax on $1,750 (at 39 percent as determined from the table) | 682.50 |
| Total tax on $15,750 | 4,232.50 |
| Tax on $14,000 (from table) | $3,210.00 |
| Tax on $1,750 (at 31 percent as determined from the table) | 542.50 |
| Total tax on $15,750 | 3,752.50 |
(b) Citizens or residents of the United States liable to tax. In general, all citizens of the United States, wherever resident, and all resident alien individuals are liable to the income taxes imposed by the Code whether the income is received from sources within or without the United States. Pursuant to section 876, a nonresident alien individual who is a bona fide resident of a section 931 possession (as defined in § 1.931-1(c)(1) of this chapter) or Puerto Rico during the entire taxable year is, except as provided in section 931 or 933 with respect to income from sources within such possessions, subject to taxation in the same manner as a resident alien individual. As to tax on nonresident alien individuals, see sections 871 and 877.
(c) Who is a citizen. Every person born or naturalized in the United States and subject to its jurisdiction is a citizen. For other rules governing the acquisition of citizenship, see chapters 1 and 2 of title III of the Immigration and Nationality Act (8 U.S.C. 1401-1459). For rules governing loss of citizenship, see sections 349 to 357, inclusive, of such Act (8 U.S.C. 1481-1489), Schneider v. Rusk, (1964) 377 U.S. 163, and Rev. Rul. 70-506, C.B. 1970-2, 1. For rules pertaining to persons who are nationals but not citizens at birth, e.g., a person born in American Samoa, see section 308 of such Act (8 U.S.C. 1408). For special rules applicable to certain expatriates who have lost citizenship with a principal purpose of avoiding certain taxes, see section 877. A foreigner who has filed his declaration of intention of becoming a citizen but who has not yet been admitted to citizenship by a final order of a naturalization court is an alien.
(d) Effective/applicability date. The second sentence of paragraph (b) of this section applies to taxable years ending after April 9, 2008.