Source classification under IRC 861, 862, and 863 is foundational to every international tax engagement. For inbound taxpayers -- nonresident aliens and foreign corporations earning income connected to the United States -- US-source classification triggers US tax jurisdiction and, in many cases, 30 percent withholding on fixed, determinable, annual, or periodical (FDAP) income. For outbound taxpayers -- US citizens, residents, and domestic corporations with operations or investments abroad -- source rules determine how much foreign-source income populates the numerator of the foreign tax credit (FTC) limitation under IRC 904, directly governing how much foreign tax can actually be credited. This guide walks through each section, the Reg. 1.861-8 expense allocation framework, FIRPTA interaction, and withholding obligations. Verify all statutory and regulatory citations at IRS.gov before relying on them in any filing or client advice.
IRC 861(a) lists the income items treated as gross income from US sources. The six principal categories are:
Interest received from a US person (individual, domestic corporation, US partnership, or the US government) is US-source income. The portfolio interest exemption under IRC 871(h) carves out qualifying interest paid to nonresident aliens from 30 percent FDAP withholding. To qualify, the obligation must be in registered form, the beneficial owner must not be a 10-percent shareholder of the payor, and the required ownership statement must be provided; verify the current portfolio interest requirements at IRS.gov.
Dividends paid by a domestic corporation are US-source income. Certain dividends paid by foreign corporations that have significant US-source earnings and profits may be partially treated as US-source under IRC 861(a)(2)(B); verify the current rules at IRS.gov. US-source dividends paid to nonresident aliens are FDAP income subject to 30 percent withholding absent a treaty rate reduction.
Compensation for personal services is US-source to the extent the services are performed within the United States. When an employee or self-employed individual works partly in the United States and partly abroad, income is allocated based on the time (days or hours) spent performing services in each jurisdiction. The IRC 861(a)(3) exception for nonresident aliens present in the United States for 90 days or fewer in a calendar year, receiving $3,000 or less from a non-US employer, may exclude the income from withholding; verify the current threshold and conditions at IRS.gov.
Rents received for the use of property located in the United States and royalties received for the use of -- or the privilege of using -- patents, copyrights, secret processes, formulas, trademarks, and similar intangibles in the United States are US-source income. Determining the geographic location of use for digital content and software licenses requires careful analysis of the applicable regulations; verify current royalty sourcing rules at IRS.gov.
Gains from the sale or exchange of US real property interests (USRPIs) are US-source income under IRC 861(a)(5). IRC 897 (FIRPTA) deems those gains, when recognized by a foreign person, to be effectively connected income (ECI) subject to graduated US tax rates. FIRPTA withholding under IRC 1445 requires the buyer to withhold 15 percent of the amount realized (verify the current rate and applicable exceptions at IRS.gov). A USRPI includes direct interests in US real property and stock in a US real property holding corporation (USRPHC); verify the current USRPHC asset ratio test and look-through rules at IRS.gov. Qualified foreign pension funds (QFPFs) are exempt from FIRPTA taxation; verify current QFPF qualification requirements at IRS.gov.
A partner's distributive share of partnership income retains the source character determined at the partnership level. If a partnership has income from US sources under IRC 861 principles, the partner's share of that income is US-source in the partner's hands. This rule applies to both foreign partners receiving US-source income (potentially subject to withholding under IRC 1446) and US partners receiving income through foreign partnerships; verify current partnership withholding and sourcing rules at IRS.gov.
IRC 861(b) provides that taxable income from US sources equals US-source gross income under IRC 861(a) reduced by the deductions that are properly allocated and apportioned to that income under Reg. 1.861-8. The expense allocation framework is mandatory and is described in detail below.
IRC 862 is the mirror image of IRC 861 for each income category:
Foreign-source income is not irrelevant to US taxpayers -- it is the numerator of the IRC 904 FTC limitation. The larger the net foreign-source taxable income (after proper expense apportionment), the greater the cap on creditable foreign taxes. Accurate sourcing directly determines whether a US taxpayer can use the foreign taxes it has paid; verify current FTC limitation rules at IRS.gov.
Foreign-source income must be classified into the correct IRC 904 basket before computing the FTC limitation. The principal baskets include general limitation income, passive category income, and -- following recent legislation -- a basket for certain net controlled transactions income (NCTI) arising from the GILTI framework changes in the One Big Beautiful Bill Act (OBBBA). Verify the current basket definitions, NCTI basket rules, and any applicable transition guidance at IRS.gov and consult independent counsel, as these provisions are recently enacted and implementation guidance may be pending.
IRC 863 governs income that does not fall entirely within either IRC 861 or IRC 862 because the income arises from activities conducted in multiple jurisdictions.
The sourcing of income from inventory sales was substantially changed by the Tax Cuts and Jobs Act of 2017. Before TCJA, the longstanding 50/50 rule under IRC 863(b) allocated income 50 percent based on where title passed (the sale) and 50 percent based on where the goods were produced (production activity). TCJA eliminated the 50/50 rule and shifted inventory sourcing entirely to production activity. Income from goods produced in the United States and sold abroad is now US-source; income from goods produced abroad and sold in the United States is now foreign-source. This change significantly affects the FTC limitation for manufacturers and distributors with cross-border production and sales.
When a taxpayer earns compensation for personal services performed partly in the United States and partly outside the United States, IRC 863 permits apportionment of the income based on time worked in each jurisdiction (typically a day-count method) or another method that accurately reflects where the services were rendered. The method used must be applied consistently and documented. Verify current personal services apportionment methods and any safe harbors at IRS.gov.
IRC 863(c) provides special sourcing rules for income from the transportation of passengers or cargo. Transportation income from a journey that both begins and ends in the United States is 100 percent US-source. Transportation income from a journey that begins or ends in the United States (but not both) is 50 percent US-source and 50 percent foreign-source. Transportation income from journeys wholly outside the United States is foreign-source. Verify current transportation sourcing rules and the interaction with the 4 percent tax on US-source transportation income of foreign corporations under IRC 887 at IRS.gov.
IRC 863(d) sources income from space and ocean activities -- including the use of satellites and activities conducted in international waters -- based on the residence of the taxpayer. Income from space and ocean activities of a US person is US-source; income of a foreign person from such activities is foreign-source. Verify current space and ocean activity sourcing rules and any applicable treaty positions at IRS.gov.
Regulation 1.861-8 is the mandatory framework for allocating and apportioning deductions between US-source and foreign-source income. Its correct application is not optional -- it is required by the statute and the regulations, and errors in apportionment directly distort the IRC 904 FTC limitation.
The regulation requires that deductions first be allocated to the class of gross income they generate, facilitate, or benefit (allocation). Within that class, the deduction is then apportioned between the statutory grouping -- the specific income group to which the Code assigns significance, typically foreign-source income under IRC 904 or a specific basket -- and the residual grouping (all other income, typically US-source income). The result is net income in each grouping after proper expense reduction.
Interest expense is apportioned using the asset method prescribed in Reg. 1.861-9 through 1.861-13. Under this method, the total interest expense of the taxpayer (or the affiliated group, for domestic corporations in a consolidated group) is apportioned between the statutory and residual groupings in proportion to the average adjusted basis of assets generating income in each grouping. A fair market value election is available; verify the current election procedures and the affiliated-group rules (which require interest apportionment on an affiliated-group basis for domestic corporations) at IRS.gov.
Research and development expenditures are apportioned under Reg. 1.861-17. The regulation requires that R&D be allocated to the geographic area in which the research is performed and then apportioned between statutory and residual groupings based on either sales or gross income in each grouping; verify the current allocation method, the exclusive apportionment option, and any elective methods at IRS.gov.
Stewardship expenses -- costs incurred by a parent company to oversee, supervise, or monitor a subsidiary -- are generally allocable only to the parent's dividend income (or deemed dividend income) from the subsidiary, not to the subsidiary's business operations. As a result, these expenses are typically not allocated to foreign-source income generated by the subsidiary's own trade or business. The characterization of an expense as stewardship versus general overhead is fact-specific. Verify current stewardship expense standards and examples at IRS.gov.
The source-of-income rules under IRC 861 through 863 and the expense apportionment rules under Reg. 1.861-8 feed directly into the IRC 904 FTC limitation. The limitation formula is:
FTC Limitation = US Tax x (Net Foreign-Source Taxable Income / Worldwide Taxable Income)
Net foreign-source taxable income is foreign-source gross income under IRC 862 minus the deductions allocated and apportioned to it under Reg. 1.861-8. Every dollar of incorrectly sourced income -- or incorrectly apportioned expense -- alters the limitation fraction and therefore the amount of foreign tax that can be credited in the current year. Excess credits may be carried back one year or forward ten years; verify current carryback and carryforward periods at IRS.gov.
US-source FDAP income paid to a nonresident alien individual or foreign corporation is subject to 30 percent withholding under IRC 1441 (individuals) or IRC 1442 (corporations), unless a reduced rate applies under an applicable income tax treaty or a Code exception applies (such as the portfolio interest exemption under IRC 871(h)). FDAP income includes dividends, interest, rents, royalties, compensation for services not treated as ECI, and similar periodic income. It does not include gain from the sale of capital assets (other than USRPI gain subject to FIRPTA under IRC 897).
Withholding agents -- any person in the chain of payment who has control of the amount paid to a foreign person -- must collect the tax at source, remit it to the IRS, and file:
Documentation requirements include a valid Form W-8BEN (individuals) or W-8BEN-E (entities) establishing the foreign person's identity and treaty eligibility, where applicable. Qualified intermediary (QI) agreements alter the withholding and reporting responsibilities of participating financial institutions. Verify current W-8 series documentation requirements, QI agreement terms, and chapter 3 and chapter 4 (FATCA) interaction at IRS.gov.
The table below summarizes the source rule and principal US tax consequence for ten income types under IRC 861 and 862. Verify all rules and current rates at IRS.gov.
| Income Type | US-Source Rule (IRC 861) | Foreign-Source Rule (IRC 862) | Key US Tax Consequence |
|---|---|---|---|
| Interest income | Paid by US obligor | Paid by non-US obligor | US-source FDAP: 30% withholding (portfolio interest exception may apply; verify at IRS.gov) |
| Dividends | Paid by domestic corporation | Paid by foreign corporation (generally) | US-source dividends to NRAs: 30% withholding or treaty rate; verify at IRS.gov |
| Personal services compensation | Services performed in the US | Services performed outside the US | US-source wages: income tax withholding; FICA may apply; verify at IRS.gov |
| Rents | Property located in the US | Property located outside the US | US-source rents to NRAs: 30% withholding on gross FDAP absent net election; verify at IRS.gov |
| Royalties | Intangible used in the US | Intangible used outside the US | US-source royalties to NRAs: 30% withholding or treaty rate; verify at IRS.gov |
| Gains from US real property | USRPI -- US-source under IRC 861(a)(5) | Foreign real property -- generally foreign-source | FIRPTA applies to foreign persons: deemed ECI; IRC 1445 withholding at 15%; verify at IRS.gov |
| Capital gains (non-real property) | Residency of seller (US resident) | Residency of seller (foreign person, generally) | NRA capital gains generally exempt from US tax absent 183-day presence rule; verify at IRS.gov |
| Inventory sales income | Production activity in the US (post-TCJA) | Production activity outside the US (post-TCJA) | Affects FTC limitation numerator for US persons; 50/50 rule eliminated; verify at IRS.gov |
| Transportation income | Begins AND ends in US (100%); begins OR ends in US (50%) | Journey wholly outside the US | Foreign corporations: possible 4% tax on US-source transportation income under IRC 887; verify at IRS.gov |
| Partnership distributive share | Determined at partnership level -- US-source share passes through to partner | Determined at partnership level -- foreign-source share passes through to partner | IRC 1446 withholding on foreign partners' US-source ECI; verify at IRS.gov |
Source classification under IRC 861 and 862 determines two fundamentally different tax outcomes depending on the taxpayer's position. For inbound taxpayers -- nonresident aliens and foreign corporations -- US-source income triggers US tax jurisdiction and, in many cases, 30 percent withholding on FDAP income under IRC 1441 and 1442; verify current withholding rates and treaty exceptions at IRS.gov. For outbound taxpayers -- US citizens, residents, and domestic corporations -- the distinction matters because foreign-source income forms the numerator of the FTC limitation fraction under IRC 904; verify current FTC limitation rules at IRS.gov. Overstating US-source income shrinks the FTC limitation and leaves foreign taxes to waste. Understating it may invite IRS scrutiny. Correct sourcing is therefore threshold work for any international engagement.
IRC 861(a) lists the six principal categories of US-source gross income: (1) interest from US obligors, subject to the portfolio interest exception under IRC 871(h); (2) dividends paid by domestic corporations; (3) compensation for personal services performed in the United States; (4) rents and royalties for US property or US-sited privileges; (5) gains from the sale of US real property interests, subject to FIRPTA under IRC 897; and (6) a partner's distributive share of partnership income to the extent the partnership has US-source income. Verify the current scope and exceptions for each category at IRS.gov.
IRC 861(b) provides that taxable income from US sources equals US-source gross income under IRC 861(a) minus the deductions that are properly allocated and apportioned to that income under Reg. 1.861-8. The regulation distinguishes two groupings: the statutory grouping (the specific income source or activity to which the Code assigns significance) and the residual grouping (all remaining income). Each expense item must be allocated to the class of gross income it generates or benefits, then apportioned between groupings using the regulatory method for that expense type. Verify current Reg. 1.861-8 allocation and apportionment rules at IRS.gov.
Regulation 1.861-8 is the master framework for allocating and apportioning deductions between US-source and foreign-source income. Key prescribed methods include: interest expense apportioned using the asset method under Reg. 1.861-9 through 1.861-13 (verify at IRS.gov); R&D expense apportioned under Reg. 1.861-17 based on sales or gross income by geographic area (verify at IRS.gov); and stewardship expenses, which are generally not allocable to foreign-source income from a subsidiary's business operations (verify at IRS.gov). Incorrect apportionment -- in either direction -- directly distorts the IRC 904 FTC limitation.
IRC 862 mirrors IRC 861 for each income category, treating as foreign-source: interest from non-US obligors; dividends from foreign corporations (generally); compensation for services performed outside the United States; rents and royalties for property or privileges used outside the United States; gains from foreign property; and a partner's share of foreign-source partnership income. Foreign-source income is the numerator in the IRC 904 FTC limitation fraction. The larger the net foreign-source taxable income (after proper Reg. 1.861-8 expense apportionment), the higher the cap on creditable foreign taxes. Verify current IRC 904 limitation rules and basket definitions at IRS.gov.
IRC 863 governs income that is partly from US sources and partly from foreign sources. The most significant change under TCJA was the elimination of the 50/50 inventory sourcing rule under IRC 863(b). Before TCJA, income from cross-border inventory sales was allocated 50 percent based on where title passed and 50 percent based on production activity. After TCJA, sourcing is entirely production-activity based: goods produced in the United States and sold abroad generate US-source income, and goods produced abroad and sold in the United States generate foreign-source income. This change materially affects the FTC limitation for manufacturers. Verify current post-TCJA inventory sourcing rules at IRS.gov and consult independent counsel, as these provisions are recently enacted and implementation guidance may be pending.
Under IRC 861(a)(5), gains from the sale or exchange of US real property interests are US-source income. IRC 897 (FIRPTA) deems those gains, when recognized by a foreign person, to be ECI taxable at graduated US rates. The IRC 1445 withholding obligation requires the buyer to withhold 15 percent of the amount realized (verify the current rate at IRS.gov). FIRPTA applies to direct real property ownership and stock in US real property holding corporations (USRPHCs); verify the current USRPHC testing threshold and look-through rules at IRS.gov. Qualified foreign pension funds are exempt from FIRPTA; verify QFPF qualification requirements at IRS.gov.
US-source FDAP income paid to nonresident aliens is subject to 30 percent withholding under IRC 1441 absent a treaty rate reduction or Code exception. Withholding agents must file Form 1042 (Annual Withholding Tax Return for US Source Income of Foreign Persons) and Form 1042-S (Foreign Person's US Source Income Subject to Withholding) for each foreign recipient. Required documentation includes a valid Form W-8BEN (individuals) or W-8BEN-E (entities). Verify current Form 1042 and 1042-S filing deadlines, W-8 documentation requirements, and QI agreement terms at IRS.gov.
Last reviewed: July 2026. This guide is for informational purposes only and does not constitute legal or tax advice. Verify all statutory citations, regulatory provisions, and guidance at IRS.gov. Consult qualified legal counsel before relying on any position.