United States Tax Residency (Substantial Presence Test)

Key parameters
Threshold	31 days current year, 183 weighted days
Period / Window	Calendar year, plus 2 prior years
Counting	Any part of a day
Additional requirements	Exempt individuals, closer connection exception

You are a US resident for tax purposes under the SPT if you meet both a 31-day floor in the current year and a 183-day weighted total across the current year plus the two before it. Both must be met in the same year — a high weighted total from past years doesn't help if you spend too few days in the US now.

Because prior years count at only a fraction of their weight, someone who visits for a similar number of days every year can gradually accumulate enough to become a resident, without ever spending 183 days in a single year.

• Exempt individuals — certain visa holders don't count their US days toward the SPT at all while exempt. Students on F, J, M or Q visas get a lifetime 5 calendar years; teachers and trainees on J or Q visas are exempt only if they weren't already exempt as a teacher, trainee or student for part of 2 of the preceding 6 calendar years.
• The closer connection exception — even if you meet the SPT, you can be treated as a nonresident if you were present under 183 days that year, kept a tax home in one foreign country all year, had a closer connection there than to the US, and weren't pursuing a green card. Claimed on Form 8840.

Meeting the SPT makes you a resident alien for the whole calendar year by default, though a first-year choice can change how part of an arrival year is treated.

• The green card test runs independently. Holding a green card makes you a US resident for tax purposes regardless of days present — the SPT is only relevant if you don't hold one.
• The closer connection exception can't rescue a green card applicant. Taking steps toward permanent residency, even informally, disqualifies you from claiming it for that year.
• Missing Form 8843 is costly. Days that would otherwise be excluded as an exempt individual or for medical reasons count anyway if the form isn't filed for that year, which can silently push someone over the 183-day weighted threshold.
• A first-year choice can split an arrival year. If you don't meet the SPT in your arrival year but will meet it the following year, you may be able to choose resident treatment for part of the current year instead of waiting.
• Weighted totals reset every year, not on a rolling basis — the test is recalculated fresh each calendar year using that year's own two-years-back window.

Getting your residency status wrong risks an accuracy-related penalty of 20% of the underpaid tax, or 75% if the Internal Revenue Service (IRS) treats it as fraud. Residency mistakes usually surface through unreported foreign accounts, where a willful failure to report carries a penalty of 50% of the account balance for each year involved. Professional tax advice is strongly recommended in situations like this.

A remote worker with no fixed pattern

You spend 200 days in the US this year, having spent 40 days last year and 30 the year before. Your weighted total is 200 + (40 ÷ 3) + (30 ÷ 6) = 218 days — over the 183-day threshold, and you also clear the 31-day floor, so you are a US resident for tax purposes this year.

A steady annual visitor

You visit the US for 120 days a year, every year, with no exempt status. In year three, your weighted total is 120 + (120 ÷ 3) + (120 ÷ 6) = 180 days — just under the threshold, so you remain a nonresident that year, but the same pattern the following year would push you over 183.

A frequent traveler under the 31-day floor

You spent 330 days in the US last year and 330 the year before, then cut back sharply to just 20 days this year. Your weighted total is 20 + (330 ÷ 3) + (330 ÷ 6) = 185 — comfortably over 183. It still doesn't matter: you never reach the 31-day floor for the current year, so you are a nonresident this year regardless of how high your weighted total runs.

• IRS — Substantial Presence Test
• IRS — Introduction to residency under US tax law
• IRS — Conditions for a closer connection to a foreign country
• IRS — Exempt individuals: Teachers and trainees