When a non-resident earns income from US sources, the IRS uses one of two completely different tax regimes. One regime treats the income like an active US business and taxes the profit at regular graduated rates. The other treats the income as passive and takes 30% off the top with no deductions. Knowing which one applies to your situation is the difference between filing a US tax return and not, between paying tax on net profit and paying tax on gross revenue, and often between owing a meaningful amount of US tax and owing nearly nothing. This is ECI vs FDAP.
ECI is income effectively connected with a US trade or business. It's taxed at graduated rates on a net basis (deductions allowed) and reported on Form 1040-NR. FDAP is passive US-source investment income. It's withheld at 30% (or treaty rate) on a gross basis (no deductions) by the US payor at the source.
The two regimes reflect a fundamental conceptual divide. If a non-resident is actively doing business in the US (running a hotel, operating a US partnership, performing services on US soil), the US claims a meaningful tax share - similar to what a US person would pay - because the income was generated through US economic activity. The IRC calls this "effectively connected" income.
If a non-resident is just collecting passive returns from US assets (dividends from US stocks, interest from US bonds, royalties on US-licensed IP), the US claims a smaller, simpler share via flat-rate withholding at the source. No tax return needed if the withholding agent gets it right. The IRS doesn't have to chase non-residents around the world to collect.
ECI is the more complicated of the two regimes - it requires actually running a tax computation - but it's also the regime that allows for meaningful deductions and lower effective rates.
Income is effectively connected with a US trade or business when it arises from active business operations in the US. The classic categories:
FDAP is the catch-all for passive US-source investment income paid to non-residents. The acronym means "fixed, determinable, annual or periodical" - which historically described how passive income gets paid (recurring, in determinable amounts) and now broadly captures most non-trade-or-business US-source receipts.
| Aspect | ECI | FDAP |
|---|---|---|
| Type of income | Active US business income, US wages, real estate gains | Passive investment income: dividends, interest, royalties, rents |
| Tax rate | Graduated (10% to 37%) | 30% statutory; treaty rate often 5-15% |
| Tax base | Net income (deductions allowed) | Gross income (no deductions) |
| Collection mechanism | Self-assessed on Form 1040-NR | Withheld by US payor at source |
| Return required | Yes - Form 1040-NR | Not required if correctly withheld |
| Treaty effect | Permanent establishment article (PE) determines whether US can tax | Reduced withholding rate; W-8BEN required |
Rental income from US real property is FDAP by default - meaning a non-resident landlord would face 30% withholding on gross rent, with no deduction for property taxes, mortgage interest, depreciation, repairs, or property management.
This produces an absurd result for a typical rental property: gross rent $30,000, expenses $25,000, net cash flow $5,000 - but 30% withholding on $30,000 gross is $9,000. The non-resident effectively loses money to the IRS each year.
The fix is the §871(d) election. By making this election, a non-resident treats US real property rental income as ECI - meaning it goes on Form 1040-NR, deductions are allowed, and the actual net income is taxed at graduated rates.
Once the §871(d) election is in place, the foreign landlord typically files Form W-8ECI with the property manager or US payor instead of Form W-8BEN. This stops the 30% gross withholding entirely - the landlord is responsible for paying tax via the 1040-NR (and quarterly estimated taxes if required).
Here's a non-obvious feature of US tax for non-residents: capital gains on personal property are generally not subject to US tax - even if the property is US-issued.
This means a Canadian investor who buys US stock through a Canadian brokerage and sells it for a gain pays no US tax on the gain. The dividend along the way is FDAP (subject to 15% treaty rate). The capital gain on sale is just not taxed by the US at all.
The general rule has limited exceptions where capital gains are US-taxable:
Most US-source interest paid to a non-resident is exempt from US tax under the "portfolio interest" exemption in IRC §871(h). This covers:
The exemption excludes interest paid on shareholder loans (because of the §881(c)(3) anti-related-party rules) and certain types of contingent interest. But for the typical non-resident investor holding US treasuries, US corporate bonds, or even US bank CDs, interest is generally tax-free at the federal level. No 30% withholding, no Form 1040-NR.
The non-resident return splits cleanly into two pages of computation:
The two computations don't mix - ECI tax and FDAP tax are calculated separately and added together.
The relevant article is generally Article VII (Business Profits), which limits US taxation of business profits to those attributable to a "permanent establishment" in the US. A non-resident with US business income but no PE - say, a Canadian consultant who travels to the US for one engagement under 183 days - may be able to claim treaty exemption from US tax on the business income via Form 8833.
This is fact-specific and the PE definition is technical (fixed place of business, agency PE, service PE - the rules differ by treaty).
Treaty rates almost always reduce the 30% statutory withholding. The recipient files Form W-8BEN with the US payor, certifying entitlement to treaty benefits and identifying the applicable treaty article. The US payor then withholds at the lower rate.
State tax does not have a parallel ECI/FDAP system. States either tax non-residents on US-source income that reaches their state nexus thresholds or they don't. The dividing line:
Make the §871(d) election early for any US rental property. Don't let the 30% gross withholding regime apply to a rental property - it almost never produces a sensible result. File Form W-8ECI with the property manager or US payor as soon as the property generates income.
File W-8BEN with every US payor of FDAP income. US brokerages, royalty payors, dividend payors. Without it, you get 30% gross withholding and have to chase the difference back. The form is simple and free.
Don't assume FDAP is "easy" because no return is required. If you've had FDAP withheld at the wrong rate (full 30% when treaty rate of 15% should have applied, for example), you need to file a 1040-NR refund return to recover the difference. The "no return required" benefit only works when withholding is correct.
For US business activity, evaluate the PE position. Many cross-border consultants and short-term US business visits don't rise to a PE under the relevant treaty. A treaty-based claim of no US tax (Form 8833 attached to a 1040-NR showing zero taxable income) is often the right answer.
Coordinate ECI with home-country tax. ECI is taxed at full graduated US rates, often reaching 24-32% federal plus state. The home-country tax credit mechanism is critical to avoid double taxation. For Canadian residents, the FTC works through Form T2209 on the Canadian T1.