Strategy Snapshot
Spend enough days in the U.S. and you become a tax resident, taxed on worldwide income, by arithmetic alone. Two forms interrupt that result: Form 8840 claims the closer connection exception for visitors under 183 days in the current year, and Form 8843 excludes the days of students, teachers, and others whose presence does not count. Both are use-it-or-lose-it filings with deadlines.
31 days in the current year plus a weighted 183-day count over three years: all of this year's days, one-third of last year's, one-sixth of the year before.
Form 8840 (closer connection) for snowbirds and frequent visitors under 183 current-year days; Form 8843 for exempt individuals whose days simply do not count; the treaty tie-breaker as the backstop.
Canadian and Latin American snowbirds who average 130-plus days a year and never file anything, quietly meeting the test with the paperwork blank.
U.S. tax residency does not require a green card, a visa category, or an intention to stay. For everyone who is not a citizen or green card holder, it is a day count, and the count is more aggressive than almost any visitor assumes. The winter residents of Florida, Canadian and Latin American alike, are the classic case: no U.S. income, no U.S. job, and a rolling three-year average of days that quietly makes them U.S. tax residents on paper, taxable on worldwide income, unless one of two short forms interrupts the result.
The stakesCrossing into U.S. tax residency does not just mean tax on U.S. income. It means worldwide income on a U.S. return, plus the FBAR and foreign asset reporting system, applied to someone who may own nothing in the United States but a condo.
The Substantial Presence Test
You meet the test for a year when both parts are true:
- You were in the U.S. at least 31 days during the current year, and
- The weighted total reaches 183 days: all of this year’s U.S. days, plus one-third of last year’s, plus one-sixth of the year before’s
Partial days count as full days: arrival day, departure day, a connection through Miami with an overnight stay. The rolling math is what surprises people. A visitor who spends 122 days every year, four months, hits 122 + 40.7 + 20.3 = 183 and meets the test perpetually. The commonly repeated “six-month rule” is only safe as a one-off; as a pattern, anything over about 120 days a year keeps you at the line every single year.
Form 8840: The Closer Connection Exception
For visitors who meet the test but spent fewer than 183 days in the U.S. in the current year, Form 8840 preserves nonresident status by establishing that your real life is elsewhere:
- Your tax home was in a foreign country all year, and
- You maintained a closer connection to that country than to the U.S., shown through the location of your permanent home, family, belongings, banks, driver’s license, voting, and the residence you list on documents
The form itself is a two-page questionnaire covering exactly those facts. Three limits matter. First, the 183-current-year-day ceiling is absolute: cross it and Form 8840 is off the table, leaving only a treaty. Second, the exception is unavailable to anyone who has applied for a green card or taken steps toward one, since a pending immigrant petition contradicts a closer connection abroad. Third, it is a deadline filing: Form 8840 goes in by the Form 1040-NR due date (attached to the return if one is due, standalone if not), and the regulations generally deny the exception to those who file late.
Form 8843: Days That Do Not Count
Form 8843 works one step earlier: rather than excusing a met test, it excludes days from the count for exempt individuals:
- Students on F and J visas, generally for their first five calendar years in the U.S.
- Teachers, trainees, and researchers on J and Q visas, generally exempt for two of the last six years
- Foreign government and international organization personnel on A and G visas
- Professional athletes competing in charitable events, and
- Anyone unable to leave because of a medical condition that arose while in the U.S.
A doctoral student can spend 365 days a year here for five years and never meet the substantial presence test, but the exclusion is claimed, not automatic: Form 8843 must be filed every year, with the tax return if one is due, or standalone by the June 15 deadline if not, even for a student with no U.S. income at all. Exempt years also do not stack indefinitely; when the student years run out, the day count starts, and the transition year (often the year an F-1 converts to an H-1B) is where residency arrives and planning is needed on both sides of the line.
If the Test Is Met and No Exception Fits
Meeting the test with no timely Form 8840 and no excludable days makes you a resident alien: worldwide income on a Form 1040, plus the FBAR and Form 8938 regimes reaching every account and asset back home. Two paths remain. Residents of treaty countries (Mexico and Canada among them) can claim the tie-breaker on Form 8833 and file as nonresidents, with that election’s own consequences. And anyone moving to the U.S. deliberately should flip the frame entirely: the year residency begins is a one-time planning window, covered in our guide to pre-immigration tax planning , where gains, entities, and account structures can be reorganized before the U.S. system attaches.
Prior years handled wrongly, worldwide income never reported by someone who had quietly become a resident, are a cleanup project, usually through the streamlined procedures for the non-willful.
When to Seek Help
A snowbird under 183 days with a stable pattern needs a day log and an annual Form 8840, and many handle that themselves. Get help when the day count is near or over the line, when a green card application coexists with foreign residence, when a student’s exempt years are ending, or when past years may already have crossed into residency with nothing filed. Residency-line questions are core work in our foreign business and investors practice , and they share one feature: every good option is a before option, and the calendar, not the IRS, is what closes them.
Last updated: 2026