Every winter, hundreds of thousands of Canadians trade snow for Florida, Arizona, and the Gulf Coast. Most of them never imagine that the time they spend down south could make them taxpayers in a second country. It can. The Internal Revenue Service uses a day-counting rule — the substantial-presence test — that catches almost every committed snowbird, and once it applies, the United States asserts the right to tax worldwide income, not just U.S. income. The good news is that a Canadian who keeps the right ties at home and files the right form, on time, almost always stays on the Canadian side of the line. The bad news is that none of it is automatic, and the one exposure that survives even a clean win — U.S. estate tax — is the one snowbirds most often overlook.
How the substantial-presence test counts your days
The substantial-presence test (SPT) is set out in section 7701(b)(3) of the Internal Revenue Code. It is a rolling three-year formula that counts:
- every day you were physically present in the United States in the current year, plus
- one-third of the days you were present in the prior year, plus
- one-sixth of the days you were present in the year before that.
If that weighted total reaches 183 days or more — and you were present at least 31 days in the current year — you meet the test, and the IRS treats you as a U.S. tax resident for the current year.
The arithmetic catches far more people than the headline "183 days" suggests, because the rolling component does the work. Consider a snowbird who spends 150 days in the United States every year. The current-year count is 150; the prior year contributes 50 (one-third of 150); the year before that contributes 25 (one-sixth of 150). The total is 225 — comfortably over the threshold. Even a moderate snowbird at 130 days a year reaches 130 + 43 + 22 = 195, still over the line. In practice, anyone who spends roughly four months or more in the United States across consecutive years will meet the substantial-presence test unless something stops it.
A day generally counts if you are physically present in the United States at any time during that day, even briefly. There are narrow exceptions — days you were unable to leave because of a medical condition that arose while you were in the country, certain days in transit, and days commuting from Canada for work under specific conditions — but for the typical snowbird, almost every day at the winter residence is a counted day.
The first line of defence: Form 8840, the closer-connection statement
The first counter-measure is the Closer Connection Exception Statement for Aliens, filed on Form 8840. It is available to a person who is not a U.S. citizen and who meets three conditions for the year:
- was present in the United States for fewer than 183 days in the current year;
- maintained a tax home in a foreign country — Canada — throughout the current year; and
- had a closer connection to that foreign country than to the United States during the year.
The "closer connection" inquiry is a facts-and-circumstances test that weighs where the centre of your life sits. The factors include the location of your permanent home, your family, your personal belongings and vehicles, your social and religious affiliations, the banks you use, where you are registered to vote, the jurisdiction that issued your driver's licence, and where you carry on business. A Canadian who keeps a year-round home in Canada, holds provincial health coverage, carries an Ontario or B.C. driver's licence, banks in Canada, and votes in Canadian elections has a strong closer-connection position.
The catch is the filing deadline and the day cap. The closer-connection exception is unavailable if you were present 183 days or more in the current year alone — so the snowbird who pushes past roughly six months in a single winter loses access to Form 8840 entirely and must look to the treaty instead. And the form must be filed by the due date for a non-resident U.S. return — generally June 15 of the following year. The IRS has taken the position that a closer-connection claim made on a late or unfiled Form 8840 can be rejected even where the underlying facts plainly support it. Filing on time, every year, is the cheapest insurance a snowbird can buy.
The second line of defence: the treaty tie-breaker
If your current-year presence is 183 days or more, the closer-connection statement is off the table and the substantial-presence test is met. The next line of defence is the Canada-U.S. tax treaty. Article IV of the Convention contains a "tie-breaker" that resolves dual residency by running through an ordered series of tests: first, the country where you have a permanent home available to you; if that is inconclusive, the country that is your centre of vital interests; then your habitual abode; and finally your citizenship.
A Canadian snowbird who keeps a permanent home in Canada, whose family, finances, and personal connections remain centred in Canada, and who is a Canadian citizen will, in the overwhelming majority of cases, tie-break to Canada under Article IV. The practical consequence is that, even though you are a U.S. resident under domestic U.S. law, the treaty allows you to be taxed by the United States only as a non-resident — on U.S.-source income — rather than on your worldwide income.
Claiming the treaty position is not silent. It requires filing a U.S. non-resident return, Form 1040-NR, together with Form 8833, the Treaty-Based Return Position Disclosure. The position is made fresh each year and must be supported by that year's facts. Asserting a treaty tie-breaker also has downstream consequences — for example, it can affect certain U.S. information-reporting obligations — so it is a step to take deliberately rather than reflexively. For a deeper walk through the day-count mechanics, see our guide on snowbirds and the substantial-presence test.
Why the closer-connection route is usually preferable
Between the two defences, the closer-connection statement on Form 8840 is the lighter touch and the one to plan for where you can. It does not require filing a U.S. tax return at all, it does not put you into the U.S. return system, and it does not create the collateral reporting consequences that can follow a treaty-based filing. The treaty tie-breaker is the stronger remedy — it works even when you have crossed 183 days in a single year, where Form 8840 is unavailable — but it asks more of you, including a non-resident return and the formal Form 8833 disclosure. The practical planning point is that a snowbird who is comfortably under 183 days in any single calendar year keeps access to the simpler route, while a snowbird who routinely pushes to the edge of the year forces themselves into the more demanding one. Many Canadians manage their travel deliberately so that no single year crosses 183 days, precisely to preserve the Form 8840 path.
It is also worth understanding what each defence does and does not accomplish. Neither one makes you invisible to the United States. Both are positions you assert and must be prepared to support if questioned, with contemporaneous records of where you were, when, and why your life remained centred in Canada. Border-crossing data, lease and mortgage documents, utility bills, provincial health enrolment, and the routine paper trail of a life lived in Canada are what carry the day if the IRS ever asks. The position is only as good as the facts and the records behind it, which is why building the habit early matters more than reacting after a notice arrives.
The trap that survives a clean win: U.S. estate tax
Here is the exposure that catches snowbirds who have done everything right on the income-tax side. Winning the substantial-presence battle keeps your worldwide income out of the U.S. system. It does nothing about U.S. estate tax, which is a separate regime with a separate trigger.
The United States imposes federal estate tax on the U.S.-situated assets of people who are not U.S. residents for estate-tax purposes, with only a US$60,000 exemption under domestic law before treaty relief. A snowbird who buys a Florida condo, keeps a car at the winter residence, holds shares of U.S. corporations in a brokerage account, or keeps art or jewellery in the United States is accumulating U.S.-situs assets. At death, those assets can draw U.S. estate tax even though the snowbird filed Form 8840 faithfully for thirty years and never owed a dollar of U.S. income tax.
The Canada-U.S. treaty softens the blow through a prorated unified credit under Article XXIX-B, calculated by reference to the ratio of U.S.-situs assets to the worldwide estate. For estates well under the U.S. unified-credit threshold, the treaty credit usually eliminates the cash tax. For larger estates — and for anyone planning around the scheduled reduction in the U.S. exemption — the math needs to be run, and there are structural responses, from holding U.S. real estate through a Canadian corporation or partnership to funding the projected exposure with life insurance. We cover this in detail on our U.S. estate tax for Canadians page, and the snowbird-specific angle on our snowbird tax planning page.
What makes this exposure easy to miss is that it operates on a completely different axis from the income-tax question. A snowbird can be a perfect non-resident for income-tax purposes — under 183 days, Form 8840 filed every year, never a U.S. return — and still leave behind an estate that owes U.S. tax simply because they bought a condo and parked a U.S. brokerage account. The two systems do not share a threshold, a form, or a defence. Defeating the substantial-presence test does nothing to the estate-tax situs analysis, and the prorated treaty credit that governs the estate-tax side has nothing to do with how many days you spent in Florida. Treating the two as one problem is the most common and most expensive error in this area.
The good news is that the estate-tax response is largely a one-time structural decision rather than an annual chore. Once a snowbird has chosen how to hold a U.S. property and how to handle U.S.-situated investments, the exposure is set and predictable. The decision is far cheaper to make before a purchase than to unwind after one, which is why the right moment to consider it is when a snowbird first thinks about buying south of the border — not years later when the estate is being administered.
What a sound snowbird routine looks like
For most Canadian snowbirds, staying organized rather than reactive is the whole game. A workable annual routine looks like this:
- Track your days. Keep a simple log of entry and exit dates each year. Border records are not always complete, and you want your own contemporaneous count if a question ever arises.
- File Form 8840 on time every year you are under 183 current-year days. It is short, it is free, and it preserves the closer-connection position.
- Watch the 183-day line in any single year. If a long winter pushes you over it, plan in advance to file Form 1040-NR with Form 8833 and assert the treaty tie-breaker rather than missing the change in posture.
- Review your U.S.-situs assets. The condo, the U.S. brokerage account, and the car at the winter home are the usual culprits. Run the estate-tax exposure before it becomes an estate's problem.
- Coordinate the two countries. Where U.S. tax does apply — on the sale of U.S. real estate, for instance — the Canadian return needs to claim the matching foreign tax credit so the same gain is not economically taxed twice.
When the filings are already behind
Some snowbirds discover the substantial-presence rules years after they should have been filing. If you have met the test in past years without filing Form 8840 or a non-resident return, the path forward depends on the facts, but it is rarely as alarming as it first appears. For Canadians who are also U.S. persons and have fallen behind on U.S. income-tax returns and information filings, the Streamlined Foreign Offshore Procedures can offer a route back into compliance without civil penalty where the prior non-compliance was not willful. Our FATCA and FBAR compliance page describes that route.
The bottom line
The substantial-presence test is built to catch the snowbird pattern, but the Canada-U.S. treaty and a timely Form 8840 are built to let committed Canadians stay Canadian. The discipline that matters is calendar discipline: count your days, file on time, and decide each year whether you are relying on the closer-connection exception or the treaty tie-breaker. And do not let an immaculate income-tax record lull you into ignoring U.S. estate tax — that is the exposure that survives even when you win every other battle. Our cross-border practice, described on our cross-border tax overview, helps Canadian snowbirds put both pieces in place before a long winter, a property purchase, or a death turns a manageable question into an expensive one.