(a) Segregation of income. This section applies for purposes of determining the tax of a nonresident alien individual who at any time during the taxable year is engaged in trade or business in the United States. It also applies for purposes of determining the tax of a nonresident alien student or trainee who is deemed under section 871(c) and § 1.871-9 to be engaged in trade or business in the United States or of a nonresident alien individual who at no time during the taxable year is engaged in trade or business in the United States but has an election in effect for the taxable year under section 871(d) and § 1.871-10 in respect to real property income. A nonresident alien individual to whom this section applies must segregate his gross income for the taxable year into two categories, namely (1) the income which is effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual, and (2) the income which is not effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual. A separate tax shall then be determined upon each such category of income, as provided in paragraph (b) of this section. The determination of whether income or gain is or is not effectively connected for the taxable year with the conduct of a trade or business in the United States by the nonresident alien individual shall be made in accordance with section 864(c) and §§ 1.864-3 through 1.864-7. For purposes of this section income which is effectively connected for the taxable year with the conduct of a trade or business in the United States includes all income which is treated under section 871 (c) or (d) and § 1.871-9 or § 1.871-10 as income which is effectively connected for such year with the conduct of a trade or business in the United States by the nonresident alien individual.

(b) Imposition of tax—(1) Income not effectively connected with the conduct of a trade or business in the United States. If a nonresident alien individual who is engaged in trade or business in the United States at any time during the taxable year derives during such year from sources within the United States income or gains described in section 871(a)(1), and paragraph (b) or (c) of § 1.871-7 or gains from the sale or exchange of capital assets determined as provided in section 871(a)(2) and paragraph (d) of § 1.871-7, which are not effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual, such income or gains shall be subject to a flat tax of 30 percent of the aggregate amount of such items. This tax shall be determined in the manner, and subject to the same conditions, set forth in § 1.871-7 as though the income or gains were derived by a nonresident alien individual not engaged in trade or business in the United States during the taxable year, except that (i) the rule in paragraph (d)(3) of such section for treating the calendar year as the taxable year shall not apply and (ii) in applying paragraph (c) and (d)(4) of such section, there shall not be taken into account any gains or losses which are taken into account in determining the tax under section 871(b) and subparagraph (2) of this paragraph. A nonresident alien individual who has an election in effect for the taxable year under section 871(d) and § 1.871-10 and who at no time during the taxable year is engaged in trade or business in the United States must determine his tax under § 1.871-7 on his income which is not treated as effectively connected with the conduct of a trade or business in the United States, subject to the exception contained in subdivision (ii) of this subparagraph.

(2) Income effectively connected with the conduct of a trade or business in the United States—(i) In general. If a nonresident alien to whom this section applies derives income or gains which are effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual, the taxable income or gains shall, except as provided in § 1.871-12, be taxed in accordance with section 1 or, in the alternative, section 1201(b). See section 871(b)(1). Any income of the nonresident alien individual which is not effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual shall not be taken into account in determining either the rate or amount of such tax. See paragraph (b) of § 1.872-1.

(ii) Determination of taxable income. The taxable income for any taxable year for purposes of this subparagraph consists only of the nonresident alien individual's taxable income which is effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual; and, for this purpose, it is immaterial that the trade or business with which that income is effectively connected is not the same as the trade or business carried on in the United States by that individual during the taxable year. See example 2 in § 1.864-4(b). In determining such taxable income all amounts constituting, or considered to be, gains or losses for the taxable year from the sale or exchange of capital assets shall be taken into account if such gains or losses are effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual, and, for such purpose, the 183-day rule set forth in section 871(a)(2) and paragraph (d)(2) of § 1.871-7 shall not apply. Losses which are not effectively connected for the taxable year with the conduct of a trade or business in the United States by that individual shall not be taken into account in determining taxable income under this subdivision, except as provided in section 873(b)(1).

(iii) Cross references. For rules for determining the gross income and deductions for the taxable year, see sections 872 and 873, and the regulations thereunder.

(c) Change in trade or business status—(1) In general. The determination as to whether a nonresident alien individual is engaged in trade or business within the United States during the taxable year is to be made for each taxable year. If at any time during the taxable year he is engaged in a trade or business in the United States, he is considered to be engaged in trade or business within the United States during the taxable year for purposes of sections 864(c)(1) and 871(b), and the regulations thereunder. Income, gain, or loss of a nonresident alien individual is not treated as being effectively connected for the taxable year with the conduct of a trade or business in the United States if he is not engaged in trade or business within the United States during such year, even though such income, gain, or loss may have been effectively connected for a previous taxable year with the conduct of a trade or business in the United States. See § 1.864-3. However, income, gain, or loss which is treated as effectively connected for the taxable year with the conduct of a trade or business in the United States by a nonresident alien individual will generally be treated as effectively connected for a subsequent taxable year if he is engaged in a trade or business in the United States during such subsequent year, even though such income, gain, or loss is not effectively connected with the conduct of the trade or business carried on in the United States during such subsequent year. This subparagraph does not apply to income described in section 871 (c) or (d). It may not apply to a nonresident alien individual who for the taxable year uses an accrual method of accounting or to income which is constructively received in the taxable year within the meaning of § 1.451-2.

(2) Illustrations. The application of this paragraph may be illustrated by the following examples:

(d) Credits against tax. The credits allowed by section 31 (relating to tax withheld on wages), section 32 (relating to tax withheld at source on nonresident aliens), section 33 (relating to the foreign tax credit), section 35 (relating to partially tax-exempt interest), section 38 (relating to investment in certain depreciable property), section 39 (relating to certain uses of gasoline and lubricating oil), section 40 (relating to expenses of work incentive programs), and section 6402 (relating to overpayments of tax) shall be allowed against the tax determined in accordance with this section. However, the credits allowed by sections 33, 38, and 40 shall not be allowed against the flat tax of 30 percent imposed by section 871(a) and paragraph (b)(1) of this section. Moreover, no credit shall be allowed under section 35 to a non- resident alien individual with respect to whom a tax is imposed for the taxable year under section 871(a) and paragraph (b)(1) of this section, even though such individual has income for such year upon which tax is imposed under section 871(b) and paragraph (b)(2) of this section. For special rules applicable in determining the foreign tax credit, see section 906(b) and the regulations thereunder. For the disallowance of certain credits where a return is not filed for the taxable year, see section 874 and § 1.874-1.

(e) Effective date. This section shall apply for taxable years beginning after December 31, 1966. For corresponding rules applicable to taxable years beginning before January 1, 1967, see 26 CFR 1.871-7(d) (Revised as of January 1, 1971).