When dealing with the international transactions, the United States tax law usually divides income into two broad categories: foreign source income and the U.S. source income. The determination of whether the income is foreign or U.S. in origin depends on a set of rules – the source-of-income rules – created by Congress, elaborated by the U.S. Treasury regulations, refined in courts, and further modified by the international treaties. While jurisdictional in nature, the income source rules are fundamentally and critically important to the understanding and operation of international transactions, primarily because these rules generate real operational consequences that affect a variety of substantive U.S. tax provisions. For the purposes of this essay, these consequences may be classified according to the grouping of the affected taxpayers.
The first set of such taxpayers are U.S. citizens, residents and domestic corporations subject to foreign tax on their income. The income source rules are crucial for these taxpayers because the U.S. foreign tax credit is available only if the foreign taxes are paid on the foreign source income. Hence, foreign taxes paid on the U.S. source income are not available to offset U.S. income tax liability. For example, suppose that a U.S. corporation earns income in the United Kingdom, which under the U.S. tax rules and relevant treaties is considered to be U.S. source income. If the U.K. authorities tax this income, the U.S. corporation will not be able to credit these taxes against the U.S. tax liability. Thus, the unfortunate result in this situation is double-taxation of the same income (note, however, that a deduction may be available to the U.S. corporation).
The other set of affected taxpayers is comprised of the nonresident aliens and foreign corporations. For this group, the impact of income source rules is two-fold. First, with respect to the business income, only U.S. source income may be regarded as effectively connected income and subject to the U.S. taxation. Hence, if the income is not a U.S. source income, then it cannot be considered as effectively connected income, thereby avoiding taxation by the U.S. government, unless the exception under I.R.C. §871(c)(4) applies. Under this exception, where certain types of income (such as dividends, interest, rents, royalties, sale of personal property, et cetera) are attributed to the nonresident alien’s (or foreign corporation’s) U.S. office or other fixed place of business, the income is regarded as effectively connected income and may be subject to the U.S. taxation.
Second, in case of non-business (usually, investment) income, the 30 percent withholding tax may be imposed only on U.S. source income. If, however, the income is considered by the U.S. tax authorities to be foreign source income, then no such tax may be imposed. For example, if a French investor receives interest that is deemed not to be U.S. source income, then the withholding tax will not be imposed.
Thus, based on the analysis above, the enormous importance of the income source rules in structuring international transactions becomes apparent. Obviously, for the purposes of illustrating their significance, I simplified this discussion into a simple domestic versus foreign dichotomy. The reality may quickly become much more complex when one takes into account various variations with respect to U.S. territories, certain types of income and/or transactions, politically-motivated exceptions regarding some foreign countries, and modification of the rules by bilateral tax treaties.
It should be remembered, however, that while they contain many traps and dangers for the unwary, the income source rules may provide excellent opportunities for beneficial and responsible tax planning.