Effectively Connected Income (ECI) Explained for Non-Residents

If you're researching US LLC taxes, you'll keep hitting three letters: ECI. It's the concept the IRS uses to decide whether — and how — a non-resident's business income gets taxed by the US. Understand ECI and the rest of the tax picture makes sense.

General information, not tax advice. Whether income is ECI is fact-specific — confirm with a qualified cross-border tax professional. Primary source: IRS: Effectively Connected Income.

What ECI is

The IRS puts it simply: when a foreign person is engaged in a trade or business in the United States, the US-source income connected to that business is Effectively Connected Income. ECI is taxed at the same graduated rates that apply to Americans — and, importantly, you can deduct expenses against it, so you're taxed on net profit.

ECI vs FDAP — the two ways the US taxes foreigners

Non-resident US income splits into two buckets, taxed very differently:

• ECI — net basis, graduated rates, deductions allowed. You report it on a return (e.g., Form 1040-NR or 1120-F).
• FDAP — passive US-source income (interest, dividends, royalties, rent). Taxed at a flat 30% (or a lower tax-treaty rate) on the gross amount, with no deductions, usually collected by withholding.

So the same dollar can be taxed on net (ECI) or gross (FDAP) depending on how it's earned. For an operating business, ECI is usually the relevant question.

The "engaged in a US trade or business" test

ECI only arises if you're engaged in a US trade or business. The IRS says the activity must be "considerable, continuous, and regular" — a one-off deal usually isn't enough. But there's no bright-line checklist. Professionals typically weigh factors like:

• Whether you perform services physically in the US;
• Whether the business has US employees or a dependent agent acting for it in the US;
• Whether it has a US office or fixed place of business.

A non-resident running an online business entirely from abroad, with no US staff or office, is often found not to have a US trade or business — but that's a fact-specific legal conclusion, not an automatic result.

Where tax treaties change the answer

If you're a resident of a country with a US tax treaty, the treaty can raise the bar: business profits are generally taxed by the US only if you have a permanent establishment (a fixed place of business like an office or branch) in the US. This "PE" standard can be more favorable than the domestic test — but only if your country has a treaty and you qualify for its benefits (usually claimed with Form W-8BEN/W-8BEN-E). No treaty means the ordinary US-trade-or-business rules govern.

Why this matters for your LLC

Whether your LLC's income is ECI is the hinge for your whole US tax position — but remember it's separate from your filing duties, which usually apply regardless (see Form 5472). For the full picture, read do foreign-owned US LLCs pay tax?. And get advice specific to your facts before relying on any single answer.