Non-Resident Alien
A non-resident alien (NRA) is a non-US-citizen who fails both the green-card test and the substantial-presence test for US tax residency. NRAs are taxed only on US-source income, typically via 30% statutory withholding on US-source dividends, interest, and certain other income (often reduced by tax treaty), with FDAP (Fixed, Determinable, Annual, Periodical) withholding rules handling most cases.
The US tax code distinguishes between resident and non-resident aliens by two tests. The green-card test: anyone with lawful permanent residence (a green card) is a resident alien for tax purposes. The substantial-presence test: anyone present in the US for 31+ days in the current year and 183+ weighted-day-equivalents across the current year and prior two years is a resident alien. A non-citizen failing both tests is an NRA.
NRA tax treatment is dramatically different from resident-alien treatment. Resident aliens are taxed on worldwide income (like citizens). NRAs are taxed only on US-source income. Most US-source passive income (dividends, interest with exceptions) is subject to FDAP withholding at 30% statutory rate, typically reduced by treaty to 10-15%. Effectively-connected income (US trade or business) is taxed at graduated rates. Capital gains on US securities are generally not subject to US tax for NRAs (a major distinction from resident treatment) — though there are exceptions for US real-estate-related and certain dividend-equivalent payments.
For wealth-tech platforms, NRA handling is the part most domestic-only platforms have a structural gap on. A platform that ingests an NRA customer as a regular US resident applies wrong tax treatment to every income item, withholds at the wrong rate, and produces wrong forms. The W-8BEN (or W-8BEN-E for entities) is the customer-supplied documentation that triggers correct NRA handling; the platform has to consume the W-8BEN data, validate it, and apply the resulting treaty-tier withholding rates.
The substantial-presence-test crossing produces a particular edge case: a non-citizen who was an NRA for some years and becomes a resident alien (typically because they accumulated enough days in the US) has dual-status filing for the year of crossing. Pre-crossing income is NRA-taxed; post-crossing income is resident-taxed. The transition produces a Form 1040 with a Form 1040-NR attached for the pre-crossing portion. Test data for cross-border platforms should include some households crossing the threshold.
Days_current + (1/3) × Days_prior + (1/6) × Days_2_years_prior ≥ 183- Days_current
- = days physically present in US in current year (must be ≥ 31)
- Days_prior
- = days physically present in US in prior calendar year
- Days_2_years_prior
- = days physically present in US two years ago
Customer present 100 days current year, 90 days prior, 90 days 2-years-prior. Test value: 100 + 30 + 15 = 145. Below 183 threshold; customer is NRA. With one more year of similar presence, customer would cross the threshold and become resident alien for that year forward.NRA-aware synthetic data needs households tagged as NRA, resident-alien, or US-citizen, with the NRA cohort having the FDAP withholding code paths exercised (US-source dividends withheld at 30% statutory or treaty rate; capital gains not US-taxed; effectively-connected income at graduated rates). Some households should cross the substantial-presence threshold during the longitudinal window to exercise the dual-status transition.
Common pitfalls
- Treating NRAs and resident aliens as one category — they have completely different tax rules.
- Applying the 30% withholding rate without checking for treaty reduction — most NRAs from treaty countries are entitled to 10-15% rates.
- Forgetting capital gains are typically not US-taxed for NRAs — applying capital-gains tax to an NRA produces a refund-claim situation.
- Missing the dual-status transition year — an NRA crossing into resident status mid-year has a complex filing requirement.
Examples
NRA customer (UK resident) holds 1,000 shares of US-listed AAPL. AAPL pays a quarterly dividend of $0.24/share = $240 gross. US-UK treaty rate on dividends: 15% (with proper W-8BEN). Withholding: 15% × $240 = $36. Net to customer: $204. Form 1042-S is issued by the broker. The customer reports the income on their UK tax return (with potential UK FTC for the US tax paid). The same dividend to a US-resident customer would be 0% withheld and reported on 1099-DIV.