Cross-Border Tax · Guide
Snowbird tax rules: the day-count formula, Form 8840, and staying a US non-resident
The IRS decides snowbird residency with a three-year weighted day count: all of this year’s US days, one-third of last year’s, and one-sixth of the year before. A typical five-to-six-month winter crosses the 183-day line almost every year — and Form 8840, filed by June 15, is what keeps you a US non-resident anyway. Count days precisely, file every year, and the pattern is safe.
By the AnalytIQ Accounting team · Last reviewed: August 12, 2026
The substantial presence test: three years, one formula
The IRS does not care that you feel Canadian — it counts days. Under the substantial presence test, you are a US resident for tax purposes if you spent at least 31 days in the US this year and your weighted three-year total reaches 183 days. The weighting: every day this year counts in full, each day last year counts as one-third, and each day the year before counts as one-sixth. Partial days count as full days — the afternoon you crossed at Buffalo counts the same as a week in Fort Myers.
Because the formula reaches back two years, a consistent winter pattern gets no credit for moderation. The same five months every year crosses the line every year.
A worked example: the five-month winter
Take a couple who spend 150 days in Arizona each winter — a typical November-to-April stay, repeated. Here is their count for the current year:
| Year | Days in the US | Fraction counted | Days that count |
|---|---|---|---|
| This year | 150 | All of them | 150 |
| Last year | 150 | One-third | 50 |
| Two years ago | 150 | One-sixth | 25 |
| Weighted total | 225 — test met (183 or more) |
225 is well past 183, so the test is met — and it will be met again next year, and the year after, for as long as the pattern holds. At a steady rhythm, any repeated pattern above roughly 120 days a year eventually crosses the line. "I'm only there five months" is not a defence; it is the exposure.
Form 8840: the exception that keeps you Canadian
Meeting the test does not make US tax residency inevitable. Form 8840, the Closer Connection Exception Statement, tells the IRS that your tax home and your life — home, family, health coverage, driver's licence, banking — remain in Canada. File it and you stay a US non-resident despite the day count. Three rules matter:
- June 15 is the deadline for a snowbird with no US wages, for each year the weighted count reaches 183.
- It is filed per person — each spouse needs their own.
- It is not available if you were actually in the US 183 days or more in the current year alone, or if you hold or have applied for a green card. Past those limits the fallback is the treaty tie-breaker claimed on a 1040-NR — a heavier, costlier filing.
File late and you can lose the exception itself. The alternative to a two-page form is being treated as a US resident taxable on worldwide income, with US foreign-account reporting attached to your Canadian bank and investment accounts. The form is cheap; the fallback is not.
The Canadian side of the ledger
Nothing above changes your Canadian residency — you remain a Canadian tax resident filing a T1 as always. But day counts run on more than one track. Provincial health plans set their own minimum days at home (the numbers vary by province — confirm yours before extending a stay), and US immigration applies its own roughly six-month admission limit that has nothing to do with the tax test. We tell clients to keep one precise travel log — border crossings, boarding passes — and let every rule be measured against it.
What we do for snowbirds: day-count review plus Form 8840
We run this as a simple annual package. Before the season we review your travel log and project the weighted count for the year ahead; after it, we prepare and file Form 8840 for each spouse ahead of June 15, and flag any year that needs more — rental income or a sale pushes you into a 1040-NR, which we prepare alongside your T1 so both countries tell one story. How we price cross-border work is set out on our fees page.
This guide covers your time — the property is its own file
Everything above is about you: whether the IRS treats you as a US resident based on where you stood each day. Owning the US home raises a separate set of questions — rental withholding, FIRPTA on sale, state filings, and US estate-tax exposure — which we cover in our snowbird US property tax guide. Most snowbird files need both answers, and they are cleanest when one team holds both.
Source: IRS — About Form 8840, Closer Connection Exception Statement for Aliens.
Common questions.
How many days can I spend in the US each year without tax trouble?
A repeated pattern under about 120 days a year keeps the weighted three-year count below 183, so the test is never met. Above that, the test is met most years — which is fine, provided Form 8840 is filed by June 15 each year. Staying under 183 actual days in any single calendar year is the hard limit that protects the exception.
What happens if I missed filing Form 8840 last year?
Do not let it sit. A late 8840 risks losing the closer-connection exception for that year, though the real exposure depends on your counts and facts. We review the past years, file what should be filed, and set the record straight before the IRS raises it first.
Is Form 8840 the same as the six-month immigration limit?
No. Immigration rules govern how long you may visit; the substantial presence test governs whether you become a US tax resident. You can be fully legal with the border officer and still meet the tax test — the two counts run separately, off the same travel log.
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