Tax
Substantial Presence Test (SPT)
Also known as: SPT, US Substantial Presence Test, 183-Day Test US
The SPT (26 U.S.C. § 7701(b)) is how the IRS decides whether a non-US-citizen, non-green-card-holder is a "resident alien" for US tax purposes — which would subject their worldwide income to US tax. The formula is mechanical:
Days in current calendar year + (Days in year–1 ÷ 3) + (Days in year–2 ÷ 6) ≥ 183 → US tax resident.
This means even reduced-presence patterns can trigger residency: 122 days/year for three consecutive years (122 + 41 + 20.3 = 183.3) makes you a US tax resident every year.
Days NOT counted toward the SPT include: days in transit (under 24 hours, US to non-US destinations); days you were in the US as a crew member of a foreign vessel; days as a teacher/trainee/student on certain visa categories (F, J, M, Q); days as a foreign-government employee; days on which you intended to leave but couldn't due to a medical condition that arose in the US.
Even if you meet the 183-day SPT threshold, you can sometimes avoid US tax residency via the Closer Connection Exception (Form 8840): if you were physically present fewer than 183 days in the current year AND have a tax home in another country AND have a closer connection to that other country than to the US (measured by location of permanent home, family, personal possessions, banking, voting, etc.). The Closer Connection Exception cannot be used if you've already applied for a green card or filed an immigrant visa petition.
For expats considering US-based work assignments, snowbird wintering, or extended visits, the SPT is the silent residency trap. A green-card-track applicant living abroad who takes 122-day annual US visits for three years suddenly becomes a US tax resident retroactively. Form 8840 must be filed by the original return due date to claim the exception — there's no late-claim mechanism.
Sources
Last factual review: 2026-05-08.
Related terms
Tax Residency
Tax residency determines which country has primary right to tax your worldwide income. Each country sets its own tests — typically based on physical presence (often 183+ days/year), domicile, primary economic interests, or family ties. Holding a residence permit does not automatically establish tax residency, and tax residency does not require a residence permit. Dual tax residency is resolved by tax-treaty tie-breaker rules.
Resident Alien
A Resident Alien is a non-US-citizen who meets either the Green Card Test or the Substantial Presence Test for US tax purposes. Resident aliens are taxed on worldwide income on the same terms as US citizens — including FEIE/FTC eligibility, FBAR/FATCA obligations, and standard Form 1040 filing. Distinct from immigration "resident alien" status (the green-card-holder term) — the IRS definition is purely fiscal.
Non-Resident Alien (NRA)
A Non-Resident Alien (NRA) is a non-US-citizen who meets neither the Green Card Test nor the Substantial Presence Test. NRAs are taxed by the US only on US-source income (typically at flat rates, often 30% gross) and on income effectively connected with a US trade or business (at standard graduated rates). Filed on Form 1040-NR. NRAs are NOT subject to worldwide-income taxation, FBAR, FATCA, or full FEIE/FTC.
FEIE (Foreign Earned Income Exclusion)
FEIE lets US citizens and resident aliens exclude up to $132,900 (2026) of foreign-earned income from US federal income tax — but not from Social Security/self-employment tax. To qualify, the taxpayer must meet either the Bona Fide Residence Test (full-year tax residence in a foreign country) or the Physical Presence Test (330 full days abroad in any 12-month period). Claimed on IRS Form 2555 attached to Form 1040.