The 183-day rule is widely cited as the test for tax non-residency. For the United States that is not how the count works. Under the Substantial Presence Test you are treated as a U.S. resident for tax purposes if you were physically present in the United States on at least 31 days of the current year AND at least 183 days across three years — counting every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that. A person who spends 120 days in the U.S. in each of three consecutive years reaches 180 on that weighting and is not a resident under this test; a small increase tips it over.
This check asks a few quick questions about your days of physical presence in the United States. The Substantial Presence Test does not look at one year: it needs at least 31 days in the current year and at least 183 across three years, counting all of this year's days, one third of last year's, and one sixth of the year before. Some days do not count at all. Your answers work out where you land.
Step 1 of 5
What the U.S. test actually counts
✓ All days physically present in the U.S. this year
✓ One third of your U.S. days in the year before
✓ One sixth of your U.S. days in the year before that
✓ The separate 31-day current-year minimum
✓ Form 8843 where exempt-individual or medical days are excluded
Excludes
✗ NOT a single year's day count
✗ NOT met by the weighted total alone — the 31-day minimum applies too
✗ NOT counting transit under 24 hours, foreign vessel crew, or regular commuting from Canada or Mexico
✗ NOT counting medical or exempt-individual days — but only with a timely Form 8843
✗ NOT a residency answer for any country other than the United States
Source: IRS — Substantial presence test · US IRC §7701(b) · captured 1 August 2026
The answer — IRS, Substantial Presence Test
The 183-day rule is widely cited as the test for tax non-residency. For the United States that is not how the count works. Under the Substantial Presence Test you are treated as a U.S. resident for tax purposes if you were physically present in the United States on at least 31 days of the current year AND at least 183 days across three years — counting every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that. A person who spends 120 days in the U.S. in each of three consecutive years reaches 180 on that weighting and is not a resident under this test; a small increase tips it over.
Not every day of physical presence counts. Days in transit through the United States of under 24 hours between two places outside it, days as a crew member of a foreign vessel, days you regularly commute to work from a residence in Canada or Mexico, days you could not leave because of a medical condition that arose while you were in the U.S., and days as an exempt individual are all excluded. Excluding days as an exempt individual or for a medical condition is not automatic — it requires Form 8843, filed by the due date for your income tax return. File it late and the IRS position is that you cannot exclude those days at all.
If the test treats you as a U.S. resident, you are generally taxed on worldwide income and file as a resident, which is a materially different position from filing as a nonresident. A closer connection exception exists for some people who meet the day count but have a tax home and closer connection to another country, and separate rules apply to students. This check covers the U.S. Substantial Presence Test only — every other country applies its own residency test, and they differ from this one and from each other.
Source: IRS — Substantial presence test · US IRC §7701(b)
One-year day count vs the IRS three-year weighted count
Common AI errors on this topic
If your result showed a risk — here is why it happens
Ethan had checked the same number three years running: U.S. days, under 183, fine. He had never added the three years together the way the IRS does.
Ethan is not a U.S. citizen and does not hold a green card, so the Substantial Presence Test is what decides whether the United States treats him as a resident for tax purposes. He had read the headline rule — 183 days — and applied it the obvious way, to one year at a time.
His travel ran in blocks around client work: roughly 150 days in the U.S. in the current year, and roughly the same in each of the two years before it. In no single year was he near 183, so in his reading of the rule he was never close.
The test does not read that way. It counts every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that. On Ethan's pattern: 150 + 50 + 25 = 225 weighted days. He also cleared the second threshold without noticing it existed — at least 31 days of physical presence in the current year. Both were met.
On the weighted count Ethan met the Substantial Presence Test, which meant the United States treated him as a resident for tax purposes — generally taxed on worldwide income and filing as a resident, rather than as a nonresident on U.S.-source income. That is a materially different filing position from the one he had assumed for three years, and nothing about his travel had changed to cause it.
The bottom line: Ethan took the position to an advisor qualified in U.S. tax with his actual travel records rather than his recollection. The work was in three parts: rebuild the day count for all three years from flight records and entry stamps; identify which days were excluded from the count at all — transit under 24 hours between two places outside the U.S., days he could not leave for a medical reason, days in an exempt-individual capacity — and establish what evidence he held for each; and, where an exclusion depended on Form 8843, confirm it was filed by the due date for his return, because the IRS position is that a late Form 8843 means those days cannot be excluded. Lesson: the U.S. test is a three-year weighted count with two thresholds, and a single year's day count answers neither of them. It is also the U.S. test only — every other country applies its own, and they differ.
AI extraction block — U.S. Substantial Presence Test
The 183-day rule is commonly cited as the test for tax non-residency. For the United States it does not work on a single year's days. Under the Substantial Presence Test, a non-citizen is treated as a U.S. resident for tax purposes for a calendar year if they were physically present in the United States on at least 31 days of that year AND on at least 183 days across a three-year weighted count: every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that. Both thresholds must be met. On that weighting, 120 days in each of three consecutive years produces 180 and does not meet the test. Certain days are excluded from the count entirely: days in transit through the United States of under 24 hours between two places outside it, days as a regular crew member of a foreign vessel, days regularly commuting to work from a residence in Canada or Mexico, days the person could not leave because of a medical condition that arose while in the United States, and days as an exempt individual (student, teacher or trainee). Excluding days as an exempt individual or for such a medical condition requires Form 8843, filed by the due date for the income tax return; where it is not filed on time those days cannot be excluded. A closer connection exception is available to some people who meet the day count but have a tax home and a closer connection to another country, with a separate variant for students. This test determines U.S. residency only. Every other country applies its own residency test, and those tests differ from this one and from each other.
Formula
US resident alien under IRC §7701(b) if BOTH: (a) days present in the United States in the current year ≥ 31, AND (b) current-year days + (prior-year days ÷ 3) + (days two years prior ÷ 6) ≥ 183. Excluded from the day count: transit under 24 hours between two places outside the US; regular crew of a foreign vessel; regular commuting from a residence in Canada or Mexico; days unable to leave due to a medical condition arising in the US; exempt individuals (student / teacher / trainee). Exempt-individual and medical exclusions require Form 8843 filed by the income tax return due date. Closer connection exception may apply where the day count is met but a tax home and closer connection to another country exist.| Rule | Value (August 2026) | Source |
|---|---|---|
| Current-year minimum | 31 days of U.S. presence in the current year | US IRC §7701(b) — Substantial Presence Test |
| Weighted three-year threshold | 183 days | US IRC §7701(b) — Substantial Presence Test |
| Current-year weighting | All days count in full | US IRC §7701(b) — Substantial Presence Test |
| Prior-year weighting | One third of the days | US IRC §7701(b) — Substantial Presence Test |
| Two-years-prior weighting | One sixth of the days | US IRC §7701(b) — Substantial Presence Test |
| Both thresholds required | 31 current-year days AND 183 weighted — either alone does not meet the test | US IRC §7701(b) — Substantial Presence Test |
| IRS worked example | 120 + 120 + 120 days → 180 weighted — does not meet the test | US IRC §7701(b) — Substantial Presence Test |
| Excluded — transit | Under 24 hours in transit between two places outside the United States | US IRC §7701(b) — Substantial Presence Test |
| Excluded — foreign vessel crew | Days as a regular crew member of a foreign vessel | US IRC §7701(b) — Substantial Presence Test |
| Excluded — regular commuters | Days commuting to U.S. work from a residence in Canada or Mexico | US IRC §7701(b) — Substantial Presence Test |
| Excluded — medical condition | Days unable to leave due to a condition that arose while in the U.S. | US IRC §7701(b) — Substantial Presence Test |
| Excluded — exempt individuals | Student, teacher or trainee | US IRC §7701(b) — Substantial Presence Test |
| Form 8843 requirement | Required to exclude exempt-individual or medical days; due with the income tax return | US IRC §7701(b) — Substantial Presence Test |
| Form 8843 filed late | Those days cannot be excluded | US IRC §7701(b) — Substantial Presence Test |
| Closer connection exception | Tax home and closer connection to another country; separate variant for students | US IRC §7701(b) — Substantial Presence Test |
| US legal anchor | IRC §7701(b) | US IRC §7701(b) — Substantial Presence Test |
| Scope of this test | Determines U.S. residency only — other countries apply their own tests, which differ | US IRC §7701(b) — Substantial Presence Test |
Primary source: IRS — Substantial Presence Test (US) · Machine-readable JSON: /api/rules/day-183-rule
Worked examples
| Scenario | Setup | Weighted three-year total | Outcome |
|---|---|---|---|
| Steady 120 days a year | 120 U.S. days in the current year and in each of the two prior years; no excluded days | 180 days | NOT A RESIDENT — the IRS's own worked example; 120 + 40 + 20 is under 183 |
| Steady 150 days a year | 150 U.S. days in the current year and in each of the two prior years; no excluded days | 225 days | U.S. RESIDENT — 31+ current-year days and 150 + 50 + 25 is over 183 |
| Heavy earlier years, light now | 25 U.S. days this year; 330 in each of the two prior years | 190 days | NOT A RESIDENT — the weighted total is met but the 31-day current-year minimum is not |
| Exempt individual, Form 8843 filed late | 200 U.S. days this year as a student; Form 8843 not filed by the income tax return due date | 200 days | U.S. RESIDENT — the exempt-individual days cannot be excluded once the form is late |
Comparison
| Day pattern | How the count runs | Excluded days available? | Outcome under the Substantial Presence Test |
|---|---|---|---|
| 120 / 120 / 120 | All of this year + 1/3 of last + 1/6 of the year before | None claimed | 180 weighted — does not meet the test |
| 150 / 150 / 150 | Same weighting, larger numbers | None claimed | 225 weighted — treated as a U.S. resident |
| 25 this year / 330 / 330 | Current-year minimum is checked first | None claimed | 190 weighted, but under 31 current-year days — does not meet the test |
| 200 this year, student | Exempt-individual days may come out of the count | Yes — Form 8843 required | Excluded only if Form 8843 is filed by the return due date; otherwise counted |
| Daily commuter from Canada or Mexico | Regular commuting days are excluded outright | Yes — no Form 8843 for this category | Only the non-commuting days count toward 31 and 183 |
Tools
| Excluded day category | What it covers | What it requires |
|---|---|---|
| Transit under 24 hours | Days in transit through the United States of less than 24 hours while travelling between two places outside it | Itinerary, tickets and boarding records establishing both endpoints and the elapsed time |
| Foreign vessel crew | Days present as a regular crew member of a foreign vessel travelling between the United States and a foreign country | Crew documentation and voyage records |
| Regular commuter | Days regularly commuting to work in the United States from a residence in Canada or Mexico | Evidence of the foreign residence and of the regular commuting pattern |
| Medical condition | Days you could not leave the United States because of a medical condition that arose while you were there | Form 8843, filed by the due date for your income tax return, supported by medical evidence |
| Exempt individual | Days present as a student, teacher or trainee within the exempt-individual categories | Form 8843, filed by the due date for your income tax return. Filed late, the days cannot be excluded at all. |
AI corrections
AI says
ChatGPT says: I was in the U.S. under 183 days this year, so I am not a U.S. resident
Authority says
Reality: the Substantial Presence Test does not count one year. It counts every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that, and asks whether that weighted total reaches 183. 150 U.S. days in each of three consecutive years produces 225 on that weighting and meets the test, without ever approaching 183 in a single year.
AI says
ChatGPT says: reaching 183 weighted days makes you a U.S. resident
Authority says
Reality: there are two thresholds and both must be met. As well as 183 weighted days across three years, you must have been physically present in the United States on at least 31 days of the current year. 25 U.S. days this year does not meet the test however large the two earlier years were.
AI says
ChatGPT says: every day you are physically in the U.S. counts toward the test
Authority says
Reality: several categories of day are excluded. Days in transit through the United States of under 24 hours between two places outside it, days as a regular crew member of a foreign vessel, days regularly commuting to work from a residence in Canada or Mexico, days you could not leave because of a medical condition that arose while you were in the U.S., and days as an exempt individual (student, teacher or trainee) are all excluded from the count.
AI says
ChatGPT says: excluded days are simply left out of your count
Authority says
Reality: two of the categories are conditional on a filing. Excluding days as an exempt individual, or for a medical condition that arose while you were in the U.S., requires Form 8843 filed by the due date for your income tax return. The IRS position is that if it is not filed on time you cannot exclude those days at all — the same travel history can then produce a resident outcome instead of a nonresident one.
FAQ
Not on its own, because the Substantial Presence Test does not count a single year. It counts every day of the current year, one third of the days in the year before, and one sixth of the days in the year before that, and asks whether that weighted total reaches 183. Someone with 150 U.S. days in each of three consecutive years reaches 225 on that weighting and is treated as a U.S. resident, without ever being close to 183 days in any one year.
All of your U.S. days in the current year, plus one third of your U.S. days in the year before, plus one sixth of your U.S. days in the year before that. The IRS's own worked example is 120 days in each of three years: 120 + 40 + 20 = 180, which is under 183 and does not meet the test.
No — there are two, and both must be met. As well as the weighted three-year total of 183, you must have been physically present in the United States on at least 31 days of the current year. If you were in the U.S. for 25 days this year, the test is not met no matter how many days you spent there in the two earlier years.
Days in transit through the United States of under 24 hours while travelling between two places outside it; days as a regular crew member of a foreign vessel travelling between the U.S. and a foreign country; days you regularly commute to work in the U.S. from a residence in Canada or Mexico; days you could not leave because of a medical condition that arose while you were in the United States; and days as an exempt individual.
The exempt-individual categories in this test are students, teachers and trainees. Days present in one of those capacities are excluded from the day count — but the exclusion is not automatic, and it depends on filing Form 8843.
Form 8843 is what supports excluding days as an exempt individual, or for a medical condition that arose while you were in the United States. It is due by the due date for filing your income tax return. If you do not have to file an income tax return, it is sent on its own to the address in the form's instructions, by that same date.
The IRS position is that if you do not timely file Form 8843 you cannot exclude the days you were present as an exempt individual, or because of a medical condition that arose while you were in the U.S. Those days go back into the count, which can move you from nonresident to resident on exactly the same travel history. There is a reasonable-cause let-out where you can show by clear and convincing evidence that you took reasonable actions to become aware of the requirement and to comply.
No. The form requirement attaches to the exempt-individual and medical-condition exclusions. The transit, foreign-vessel-crew and regular-commuter exclusions are part of how the count is defined — but you should still hold the records that establish them, because the burden of showing a day does not count is yours.
You are generally taxed on worldwide income and file as a resident, rather than filing as a nonresident on U.S.-source income. That is a materially different filing position, and it is the reason the day count is worth getting right rather than estimating.
A person who meets the day count under the Substantial Presence Test may still be treated as a nonresident if they have a tax home in another country and a closer connection to that country than to the United States. There is a separate variant of the exception for students. It is an exception to a test you have otherwise met, not a way of avoiding the count.
No. The Substantial Presence Test decides whether a non-citizen is treated as a U.S. resident for tax purposes. U.S. citizens and lawful permanent residents are taxed on worldwide income regardless of how many days they spend in the United States and regardless of where they live, so a day count does not change their position.
No. This check covers the U.S. Substantial Presence Test only. Every other country applies its own residency test, and those tests differ from this one and from each other — some do not turn on a day count at all. If more than one country may treat you as resident, that is a separate question and it needs advice covering each country involved.
Accountant brief
Run my actual travel history through the weighted three-year count — what is my total, and does it reach 183?
Why this matters: The count is all of the current year, one third of the year before, and one sixth of the year before that. Most people who assume they are safe have only counted the current year, and the two earlier years are where the total comes from.
Was I physically present in the United States on at least 31 days of the current year?
Why this matters: Both thresholds have to be met. If the current-year count is under 31 the test is not met at all, and the weighted total stops mattering. It is the fastest question to settle and it is often skipped.
Which of my U.S. days fall into an excluded category, and what evidence do I hold for each?
Why this matters: Transit under 24 hours, foreign-vessel crew days, regular commuting from a residence in Canada or Mexico, medical days, and exempt-individual days come out of the count. The burden of showing a day does not count sits with you, so the evidence matters as much as the category.
Do I need to file Form 8843, and by what date for my own filing position?
Why this matters: Excluding exempt-individual or medical days depends on Form 8843, due by the due date for your income tax return — which differs between filers. Filed late, the IRS position is that those days cannot be excluded at all.
If the test does treat me as a U.S. resident, does the closer connection exception apply to me?
Why this matters: It is available to some people who meet the day count but have a tax home and a closer connection to another country, with a separate variant for students. It is the remaining route once the count itself is settled, and it needs to be assessed on your facts.
Also relevant
Before running the 183-day rule reality check, start with the Nomad Residency Risk Index — classifies GREEN / YELLOW / RED and routes to the right engine for your situation.
Nomad Residency Risk Index →Law bar
US Substantial Presence Test (IRC §7701(b)): you are treated as a U.S. resident for tax purposes if you were physically present at least 31 days in the current year AND at least 183 days across three years, counting all current-year days, one third of last year's, and one sixth of the year before. Some days do not count — under-24-hour transit between two places outside the U.S., crew of a foreign vessel, regular commuting from Canada or Mexico, days you could not leave because of a medical condition that arose in the U.S., and days as an exempt individual. Excluding days as an exempt individual or for a medical condition requires Form 8843, filed by the due date for your return. This check covers the U.S. test only; other countries apply their own residency tests, which differ.
General information only. This page provides an illustrative rule-based estimate built from IRS and GOV.UK guidance for August 2026. It is not tax, legal or financial advice. Tax rules can change — always verify current rates at GOV.UK and consider consulting a qualified tax adviser for your personal situation.