United States (Federal) tax residency rules
Threshold: 183 days · Substantial Presence · Calendar year (Jan 1 – Dec 31)
The United States Substantial Presence Test (SPT) determines US tax residency for non-citizens. The 3-year weighted formula counts current-year days at full weight, prior-year days at 1/3, and two-years-prior days at 1/6. Cross 183 weighted days (with at least 31 in the current year) and you're a US tax resident — taxed on worldwide income.
- Closer-connection exception (Form 8840) preserves non-resident status for those with stronger foreign ties.
- Treaty tie-breakers in US treaties decide residency when both the SPT and a foreign rule apply.
- Exempt individuals (F/J/M students, A/G visa holders, J/Q teachers) exclude their US days entirely.
Rules tracked by Tax Days
Substantial Presence Test
- Type
- Substantial Presence
- Threshold
- 183 days
- Period
- Calendar year (Jan 1 – Dec 31)
A 3-year weighted formula: current-year days, plus 1/3 of prior-year days, plus 1/6 of two-years-prior days. Threshold is 183 weighted days.
3-year weighted formula: all days current year + 1/3 prior year + 1/6 two years prior. You meet the test if the total is ≥ 183.
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