Canadian Snowbirds and the US 183-Day Rule: The Formula, Form 8840 and the Real Limits (2026)

Every autumn, hundreds of thousands of Canadians head to Florida and Arizona believing one number keeps them safe: "under six months". The US tax system does not work that way. The Substantial Presence Test counts your days with a three-year weighted formula, which means a consistent snowbird pattern of well under six months can still make you a US tax resident on paper. Here is the actual math, the escape hatch most snowbirds should be filing, and the records that make it painless. Updated 5 August 2026.

The test, in the IRS's words

"You will be considered a United States resident for tax purposes if you meet the substantial presence test for the calendar year."
— IRS, Substantial Presence Test (accessed 5 August 2026)

The test is met with at least 31 days in the current year and 183 weighted days across three years, counting "all the days you were present in the current year, and 1/3 of the days you were present in the first year before the current year, and 1/6 of the days you were present in the second year before the current year".

Why "under six months" fails

Run the formula on a steady snowbird pattern of 150 days every winter: 150 + 50 + 25 = 225 weighted days. Comfortably over 183, despite never coming close to six months in any single year. The break-even for a repeating annual pattern is about 121 days (121 + 40.3 + 20.2 ≈ 182), which is where the snowbird "120-day rule of thumb" comes from: stay under roughly four months every year and the formula stays under 183. Between 121 and 182 days a year, you likely meet the test and need the escape hatch below. Part days count, including arrival and departure days.

The escape hatch: the closer connection exception (Form 8840)

Meeting the formula does not have to mean filing US resident taxes. If you were present fewer than 183 days in the current year, maintain a tax home in Canada and have a closer connection to Canada, you can claim the closer connection exception by filing Form 8840 each year, by the filing deadline. Many long-standing snowbirds should be filing it annually and are not. Note the hard edge: at 183+ actual days in the current year the exception is unavailable, and treaty relief becomes the (much more involved) fallback.

Do not forget the state layer

Florida has no state income tax, which is much of its charm. But snowbirds splitting time across states, or wintering in states that do tax, should know the state day-count rules are separate from the federal formula: see our state-by-state day-count table (Arizona, for instance, presumes residency past nine months, while other states trigger at 183). Canadian provincial health coverage also imposes its own minimum-days-at-home rules, another reason the count matters in both directions.

Track the winters properly

The formula needs three years of accurate day counts, and Form 8840 asks for them explicitly. Check your position with our free Substantial Presence Test calculator, and keep the running count with the Days Monitor iPhone app: it logs days automatically, applies the weighted SPT formula in its USA template, warns you as winters stack up, and exports the timestamped record your cross-border accountant wants. Download it on the App Store.

Sources

• IRS, Substantial Presence Test (accessed 5 August 2026)
• IRS, About Form 8840, Closer Connection Exception Statement for Aliens (accessed 5 August 2026)

This article is general information, not legal, tax or immigration advice. Rules and their enforcement change, and your facts matter. Verify current requirements with the official sources linked above and confirm your position with a qualified professional.

British readers: the same formula applies to UK snowbirds, with a visa wrinkle on top. See British snowbirds in Florida.