A foreign corporation earning income connected with the United States has a filing obligation here, and the way that income is characterised decides almost everything that follows.
The form itself is manageable. What tends to be difficult is evidence: the records supporting the characterisation usually sit in another country, were prepared for another purpose, and sometimes in another language.
This covers who has to file, the distinction the return turns on, how treaty positions are taken, and why filing late is materially better than not filing at all.
Foreign corporations that earn income from US sources must report that income to the IRS using Form 1120-F. The form has two separate tracks depending on whether the income is effectively connected with a US trade or business. This guide explains who files, when to file, and how to navigate the form's most complex provisions.
Who Must File Form 1120-F
- Any foreign corporation that was engaged in a trade or business in the US at any time during the tax year
- Any foreign corporation that had income, gains, or losses treated as effectively connected with a US trade or business (ECI)
- Any foreign corporation that had US-source income subject to withholding tax (even if it had no ECI)
- Foreign corporations claiming a refund of withholding tax
- Foreign corporations claiming treaty benefits to reduce withholding rates
A foreign corporation that had no US income and was not engaged in a US trade or business generally does not need to file, but may need to file a protective Form 1120-F to preserve the right to claim deductions if the IRS later asserts ECI.
The difficulty here is almost never the form. It is that the records supporting how the income was characterised sit abroad, sometimes in another language, and were never assembled with a US filing in mind. Decide what evidence you would produce if asked, and keep it where it can be produced.
Ankit Sarawagi, CPA, CA, MBA · LinkedInECI vs. Non-ECI Income: The Core Distinction
Effectively Connected Income (ECI)
Income that is effectively connected with the conduct of a US trade or business is taxed at graduated rates (or the flat 21% corporate rate) after allowable deductions. ECI is reported in Section I of Form 1120-F.
- Business income from US operations
- Gains from disposition of US real property interests (FIRPTA)
- Income elected to be treated as ECI (e.g., certain interest income)
Non-ECI US-Source Income
Passive income from US sources, dividends, interest, rents, royalties, and similar items, is not ECI and is taxed at a flat 30% withholding rate (or reduced treaty rate) under FDAP (Fixed, Determinable, Annual, or Periodic). This income is reported in Section II of Form 1120-F.
Filing Deadline
| Situation | Deadline |
|---|---|
| Foreign corp engaged in US trade or business | 15th day of 4th month after end of tax year (April 15 for calendar year) |
| Extension (Form 7004) | Automatic 6 months |
| Foreign corp NOT engaged in US trade or business but with US-source income | 18th day of 6th month after end of tax year (June 18 for calendar year) |
Key Sections of Form 1120-F
Section I: ECI
- Income: gross ECI receipts, cost of goods sold, other income
- Deductions: expenses allocable to ECI under Treas. Reg. 1.882-4 (interest expense allocation rules are complex)
- Tax computation at US corporate rates
Section II: FDAP / Non-ECI
- Reports US-source income not effectively connected with US business
- Tax at 30% (or reduced treaty rate)
- Credits for tax withheld at source
Section III: Branch Profits Tax
Foreign corporations operating through a US branch (rather than a subsidiary) may owe a 30% branch profits tax on the dividend equivalent amount, the portion of ECI that is repatriated to the foreign home office. Treaty exemptions and reductions often apply.
Treaty Positions
If a foreign corporation is claiming a reduced rate or exemption under a US tax treaty, it must:
- Complete Schedule P (List of Shareholders) if applicable
- Complete the relevant treaty disclosure section
- Potentially file Form 8833 (Treaty-Based Return Position Disclosure) for certain positions
Pro Tip: Claiming treaty benefits does not eliminate the filing obligation, Form 1120-F must still be filed.
Interest Expense Allocation
Deductions for interest expense are subject to complex allocation rules under Treas. Reg. 1.882-5. Foreign corporations must allocate interest based on the ratio of US assets to worldwide assets. This is a frequent area of IRS scrutiny for large multinationals.
Common Mistakes
- Failing to file a protective return, if the IRS later asserts ECI, deductions are disallowed if no return was filed
- Incorrect classification of income as ECI vs. non-ECI
- Missing branch profits tax, often overlooked for branch operations
- Incorrect interest allocation under the asset method
- Not disclosing treaty positions on Form 8833 when required
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Frequently Asked Questions
Does a foreign corporation with only FDAP income need to file 1120-F?
It depends on whether withholding was correctly applied. If all FDAP income had proper withholding and no refund is claimed, filing may not be required. However, filing may be beneficial to claim deductions or treaty benefits.
What is FIRPTA and how does it affect Form 1120-F?
FIRPTA (Foreign Investment in Real Property Tax Act) treats gains from the disposition of US real property interests as ECI. The buyer is typically required to withhold 15% (or 21% for corporations in some cases), VERIFY current rate. The foreign corporation claims a credit for this withholding on Form 1120-F.
Can a foreign corporation avoid branch profits tax entirely?
Yes, if the applicable tax treaty eliminates branch profits tax. Also, reinvesting US profits in the US branch reduces the dividend equivalent amount.
What records does a foreign corporation need to keep in the US?
Enough to support how income was characterised and how expenses were allocated, and available if they are asked for. The characterisation question is the one that drives the return, so contemporaneous evidence of what the business actually did in the country, who did it and under what contracts is the core of it. Records kept only abroad and only in another language regularly become the difficulty rather than the position itself.
What happens if a return is not filed at all?
More than a late filing penalty, which is the part that surprises people. Deductions and credits against effectively connected income generally have to be claimed on a timely filed return, and the ability to claim them can be lost where no return is filed. The result is that tax can be computed on gross rather than net amounts. That is why filing, even late and even at a loss, is materially better than not filing.
Written by
Ankit Sarawagi, CPA, CA, MBA
Ankit leads the finance team at Profitjets, where he has worked with 500+ businesses across the US on bookkeeping, tax and CFO-level strategy. He writes about the habits that keep small business books accurate all year. Connect on LinkedIn
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