How many days can a Canadian stay in the US?

The short answer is that there is no single fixed number. What the IRS actually runs is a weighted formula across three calendar years — and the math can catch you off guard if you are only watching the calendar for the current season.

Here is how it works.

The Substantial Presence Test

The IRS counts your US days using a rolling three-year formula:

- Every day you spend in the US this year counts as a full day. - Every day you spent in the US last year counts as one-third of a day. - Every day you spent in the US the year before that counts as one-sixth of a day.

If that weighted total reaches 183, the IRS can treat you as a US tax resident for the current year — even if you never came close to 183 days in any single calendar year.

The practical implication: a snowbird who spends 150 days a year in Florida or Arizona is not in obvious danger this year, but the compounding effect of prior years is real. After a few seasons, a pattern of 120 to 130 days per year can push the weighted total toward the threshold faster than people expect.

A rough rule of thumb that most cross-border tax advisors use: staying under about 120 days in any given year keeps the three-year weighted total well under 183, assuming similar patterns in prior years. But the exact safe number depends on your own history, so run the math against your actual travel record.

What happens if you cross 183 weighted days?

Crossing the threshold does not automatically mean you owe US taxes on everything. It means the IRS considers you a resident alien for that tax year — which triggers US filing obligations and potentially tax on worldwide income. That is a significant change from the non-resident status most Canadians assume they hold.

Two things can help, but neither is automatic.

The first is the Closer Connection Exception. If you spent fewer than 183 days physically in the US during the current year (not the weighted count — actual days), and you can demonstrate that your primary connections remain in Canada — your permanent home, your family, your banking, your provincial health plan, your driver's licence, your social ties — you may qualify to file IRS Form 8840 and claim that exception. Filing Form 8840 is how you document and protect that status. Missing the filing deadline forfeits the exception for that year.

The second is the Canada-US Tax Treaty tie-breaker rule. It exists for situations where both countries could claim you as a resident. Applying the tie-breaker is more complex than filing Form 8840 and usually requires professional help.

Neither path is a loophole. Both require accurate records and timely filing.

The day-counter in Being Canadian

The Being Canadian app tracks your US days against the three-year weighted formula in real time. You can see your weighted total today, project whether a planned trip pushes you closer to the threshold, and keep a record of your travel history that you can hand to a tax professional at year-end.

It does not replace advice. It does make that conversation faster and more accurate.

What this post is, and what it is not

This is general information about how the IRS Substantial Presence Test works. It is not legal advice, tax advice, or a substitute for guidance from a cross-border tax professional who knows your specific situation. The rules described here are based on publicly available IRS guidance and are accurate to the best of our knowledge as of the date of this post, but tax rules change and your circumstances are individual.

If you are spending significant time in the US, please talk to a cross-border tax accountant before assuming your status.

You belong.