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.
United States (Federal) tax residency, FAQ
How does United States (Federal) count days for residency?
United States (Federal) uses a weighted multi-year formula rather than a simple count: all days this year, one-third of last year's days, and one-sixth of the year before. Crossing 183 weighted days generally triggers residency. 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.
How does United States (Federal) count a day of presence?
Day-counting rules vary: many jurisdictions treat any part of a calendar day spent in-country as a full day, while others require presence at midnight. Because the burden of proof is usually on you, keep a contemporaneous, day-by-day record of where you were.
What tax year does United States (Federal) use?
United States (Federal) measures residency over calendar year (jan 1 – dec 31).
Related guides
- Federal
How the Substantial Presence Test works: the rule, the exemptions, and the math
The IRS Substantial Presence Test is a 3-year weighted day count deciding whether non-citizens are US tax residents. The rule, the exemptions, and the result.
- Federal
The SPT 3-year weighted formula, with worked examples
The IRS Substantial Presence Test uses a 3-year weighted day-count formula. Here it is in plain math, with worked examples for visas and travel patterns.
- Federal
Form 8840 and the closer-connection exception
Even if you meet the IRS Substantial Presence Test, you can avoid US tax-resident status by claiming closer connection on Form 8840, if you qualify for it.
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