REFERENCE
Resident alien vs. nonresident alien: the line that decides your US taxes
"Resident alien" is a tax status, not an immigration one, and it carries the biggest consequence in the US code: resident aliens are taxed like citizens, on their worldwide income. Nonresident aliens are taxed only on US-source income. Which side of the line you are on is decided by two mechanical tests, and one of them is a day count.
The two ways you become a resident alien
- The green card test. Lawful permanent residents are resident aliens from their first day of presence as such, regardless of day counts. The status persists for tax purposes until formally abandoned.
- The Substantial Presence Test. Enough US days: at least 31 this year, and a weighted three-year total of 183 (this year's days + 1/3 of last year's + 1/6 of the year before's). Read the full SPT explainer or run the calculator.
Your visa category matters only at the edges: students and certain exchange visitors on F, J, M, or Q visas can exclude "exempt individual" days for a limited number of years (filing Form 8843), which delays but does not prevent the day count from starting.
What each status pays
Resident aliens file Form 1040 like citizens: worldwide income, graduated rates, and the same reporting obligations, including foreign-account reporting. Nonresident aliens file Form 1040-NR and are taxed only on US-source income, in two buckets: income effectively connected with a US trade or business at graduated rates, and passive US-source income (dividends, certain interest, royalties) generally at a flat 30% unless a treaty lowers it, usually collected by withholding. Foreign wages and foreign investment income sit outside the US net entirely.
Dual-status years and the escapes
The year you arrive or leave is typically a dual-status year: nonresident for part, resident for part, with residency start-date rules keyed to your first day of presence and restrictions (no standard deduction, generally no joint return) that surprise people. And meeting the SPT is not always the end: with under 183 actual current-year days, a foreign tax home, and closer connections abroad, Form 8840 preserves nonresident status; tax-treaty tie-breakers can do the same.
Why the day record is the whole game
For anyone without a green card, this entire status question reduces to day arithmetic across three years, and the 8840 escape adds a second count (actual days under 183). Those are exactly the numbers people guess at in April. SpyglassBeacon counts US days automatically, keeps the multi-year history, and exports the timestamped record the determination runs on.
Frequently asked questions
What does resident alien mean?
A non-citizen taxed like a citizen: worldwide income, regular rates. You get there via a green card or the Substantial Presence Test.
Does my visa type make me one?
No; days do. Certain student and exchange visas exclude days for a while, which delays the count rather than preventing it.
How are nonresident aliens taxed?
US-source income only: effectively connected income at graduated rates on 1040-NR, passive US income generally at a flat 30% or treaty rate via withholding.
Can I be both in one year?
Yes, dual-status: common in arrival and departure years, with its own filing mechanics.
Not tax advice. Treaties, exempt-day categories, elections like first-year choice, and dual-status mechanics are fact-specific. Confirm your situation with a qualified adviser.
Sources: IRS, determining tax residency status; IRS, taxation of nonresident aliens.
Related: Nonresident alien: the deep dive · The Substantial Presence Test · SPT calculator · US taxes for Americans abroad · Canadian snowbirds
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