Substantial Presence Test vs. Green Card test: how the two trigger US tax residency
Non-citizens become US tax residents under either the Substantial Presence Test or the Green Card test. How each works, and what happens when both apply.
The IRS uses two separate tests to determine US tax residency for non-citizens: the Substantial Presence Test (SPT) and the Green Card test. They operate independently, meeting either makes you a US tax resident. Once a tax resident, you're taxed on worldwide income.
The Green Card test
If you've been issued a green card (lawful permanent resident status), you're a US tax resident from the day you arrive in the US with that status. It doesn't matter how few days you spend in the US, your status is the trigger. You remain a tax resident under the Green Card test until either:
- Your status is rescinded or judicially or administratively determined to have been abandoned.
- You file a written abandonment of LPR status (Form I-407).
- You're a long-term resident who applies the treaty tie-breaker to be treated as a non-resident (this is a 'covered expatriate' event with potential exit-tax consequences).
Many green-card holders living abroad assume their tax obligation ends when they stop spending time in the US. It does not. The Green Card test continues until you formally abandon LPR status, and abandonment can trigger exit tax consequences if you're a long-term resident.
The Substantial Presence Test
If you don't have a green card, the SPT determines your status. The SPT is a 3-year weighted day-count formula: current-year days × 1, plus prior-year days × 1/3, plus two-years-prior days × 1/6. Crossing 183 weighted days (with at least 31 in the current year) triggers residency.
What happens when both could apply
If you have a green card AND meet the SPT, the Green Card test typically governs. The two don't conflict, you're a US tax resident under both. The practical implications are similar (worldwide income taxation), but documentation differs slightly, and treaty tie-breakers may apply differently.
Treaty tie-breakers
Even if the Green Card test or SPT makes you a US tax resident, a treaty tie-breaker can place your residency in another country. This is called 'treaty-resident status' and is reported via Form 8833. For green-card holders, treaty residency in another country can still leave you with US tax obligations on certain US-source items.
Long-term green-card holders applying treaty tie-breakers must consider exit-tax exposure. If you're a 'covered expatriate' under IRC § 877A, the gain-realization exit tax can apply.
Documentation that matters for both tests
- Day-count log of US presence (foundational for SPT, supportive for treaty tie-breaker).
- Form I-94 records (US arrival/departure history).
- Form 8840 (Closer Connection Exception) if you meet the SPT but qualify for the exception.
- Form 8833 (Treaty-Based Return Position Disclosure) if you're claiming treaty residency.
- Form I-407 (Abandonment of LPR Status) if applicable.
Track US days carefully
Tax Days tracks US days for the SPT and supports green-card holders who want a contemporaneous record of US presence (for treaty-tie-breaker positions, abandonment timing, or exit-tax planning). The 3-year SPT formula updates in real time.
Frequently asked questions
Do I pay US taxes if I have a green card but live abroad?
Generally yes. Under the Green Card test you're a US tax resident from the day you arrive in the US with lawful permanent resident status, no matter how few days you actually spend there. That obligation continues until your status is rescinded, judicially or administratively determined abandoned, or you file a written abandonment on Form I-407.
What is the difference between the Substantial Presence Test and the Green Card test?
The Substantial Presence Test is a day-count test: a 3-year weighted formula (current-year days, plus one third of prior-year days, plus one sixth of days two years prior) that generally triggers residency at 183 weighted days with at least 31 days in the current year. The Green Card test is status-based: holding lawful permanent resident status makes you a tax resident regardless of days. Meeting either test makes you a US tax resident taxed on worldwide income.
What happens if I meet both the Green Card test and the Substantial Presence Test?
The two tests don't conflict: you're a US tax resident under both, and the Green Card test typically governs. The practical result, worldwide income taxation, is similar either way, though documentation differs slightly and treaty tie-breakers may apply differently.
Can a tax treaty override US tax residency?
Generally yes. Even if the Green Card test or SPT makes you a US tax resident, a treaty tie-breaker can place your residency in another country, a position disclosed on Form 8833. For green-card holders, treaty residency elsewhere can still leave US tax obligations on certain US-source items, and long-term residents who apply a tie-breaker can face exit-tax exposure as covered expatriates under IRC Section 877A.
How does a green card holder stop being a US tax resident?
Generally by formally ending lawful permanent resident status: filing a written abandonment (Form I-407), having the status rescinded or determined abandoned, or, for long-term residents, applying a treaty tie-breaker to be treated as a non-resident. Simply moving abroad and spending no time in the US does not end the obligation, and abandonment by a long-term resident can carry exit-tax consequences.