What Is the Substantial Presence Test?
The Substantial Presence Test is a US federal tax residency rule under which foreign nationals become resident aliens through a weighted count of physical-presence days.
Also known as: SPT, US 183-Day Test.
How Substantial Presence Test works
The Substantial Presence Test is the day-count rule the IRS applies to non-citizens without a green card to decide whether they are US resident aliens for a calendar year, which brings worldwide income into US taxation, or non-resident aliens taxed mainly on US-source and effectively connected income. Two thresholds must both be met: at least 31 days of physical presence in the current year, and at least 183 weighted days across a three-year window. The weighted count adds every day in the current year, one third of the days in the first preceding year and one sixth of the days in the second preceding year. Days spent as an exempt individual, such as qualifying students, teachers, trainees and certain diplomatic staff, are excluded, and Form 8843 is generally used to support the exclusion. Meeting the test is not always final: the closer connection exception, treaty tie-breaker rules and dual-status rules for arrival and departure years can change the outcome, subject to filing and eligibility conditions.
Substantial Presence Test vs Green Card Test
Unlike the Green Card Test, which makes a lawful permanent resident a US tax resident regardless of days spent in the country, the Substantial Presence Test depends entirely on counted physical-presence days.
| Substantial Presence Test | Green Card Test | |
|---|---|---|
| Trigger | Weighted count of days physically present in the United States | Holding lawful permanent resident status at any time in the year |
| Who it targets | Visitors, workers and other non-citizens without a green card | Green card holders, whether or not present in the United States |
| Ways out | Exempt-individual days, closer connection exception, treaty tie-breaker | Formal abandonment or rescission of status, or treaty tie-breaker, with possible expatriation consequences |
Example
Illustrative example: A remote software consultant who is a citizen of Country A spends 120 days in the United States in each of three consecutive years. Under the IRS formula, the current year counts 120 days, the first preceding year adds 40 and the second preceding year adds 20, for a weighted total of 180 days, so the 183-day threshold is not reached in the third year. If the consultant instead spends 130 days in the third year, the weighted total becomes 190 days and the test is met, even though the consultant never spent half of any single year in the country. The consultant may then examine whether a tax home and closer connection in Country A support the closer connection exception, or whether the treaty between Country A and the United States assigns residence to Country A under its tie-breaker rules. Each route has its own filing requirements, and the result also affects state tax exposure, information reporting such as FBAR and Form 8938 filings, and the treatment of foreign accounts, pensions and companies held in Country A. A wrong assumption about residence status in one year can therefore carry forward into the following years, because each later calculation reuses the same weighted three-year window.
Common misconception
Myth: Staying under 183 days in each calendar year keeps a foreign visitor from becoming a US tax resident.
Reality: The Substantial Presence Test weights days across three years, so regular stays of about four months a year can exceed the 183-day threshold without any single year reaching it.
Frequently asked questions
How is the substantial presence test calculated?
The Substantial Presence Test adds all days in the current year, one third of the days in the first preceding year and one sixth of the days in the second preceding year; the total must reach 183, with at least 31 current-year days.
Can a person meet the substantial presence test and still be a nonresident?
A person meeting the Substantial Presence Test may still be treated as a non-resident alien through the closer connection exception or a tax treaty tie-breaker rule, provided the conditions and required disclosures are satisfied.
Which days do not count toward the substantial presence test?
Days as an exempt individual, including qualifying students, teachers, trainees, certain foreign government staff and professional athletes at charitable events, are excluded from the Substantial Presence Test, along with certain other limited categories of days.
Does the substantial presence test apply to US citizens?
The Substantial Presence Test applies only to non-citizens; US citizens are taxed on worldwide income under citizenship-based taxation regardless of where or how long they live abroad.
Related terms
- Green Card Test — Alternative route to US resident alien status
- Resident Alien — Status produced by meeting the test
- Dual Status Alien — Status in arrival or departure years
- Tie-Breaker Rule — Treaty rule that can override the result
Related guides
- Global tax reform and US digital nomads — US tax context for mobile workers
- Tax treaties and international taxation — How treaties resolve dual residence
Sources
Last verified: 2026-10-09. This entry is general information, not tax or legal advice; rules vary by country and change over time.
