How does the Canada-US tax treaty decide which country I am a resident of?

The tie-breaker only starts once both countries claim you

Each country decides residency under its own law first. Canada treats you as a resident if your significant residential ties — a home, a spouse or partner, dependants — are here, or deems you resident if you sojourn in Canada for 183 days or more in a year. The US treats you as a resident if you are a citizen, hold a green card, or meet the substantial presence test on days spent in the US. When both sets of rules capture the same person in the same year, that person is a dual resident, and Article IV(2) of the Canada-US tax treaty exists to break the tie.

The people who most often need it are green card holders and US citizens' spouses who have settled in Canada, Canadians who have taken US jobs but kept a family home here, and heavy US travellers who trip the substantial presence test. Our companion answer on Canadians working in the US covers the wage side of that last group.

The four tests run in strict order, and most cases end at the second

1. Permanent home. You are resident where you have a permanent home available to you. A home is any dwelling kept for your continuous use, owned or rented; a hotel room or a friend's spare bed is not. If you have a home in both countries, or in neither, move to the next test.
2. Centre of vital interests. You are resident where your personal and economic relations are closer. Where your spouse and children live, where you work or run a business, where your bank accounts, investments, memberships and doctors are, and where you spend your social life all count. This is where most files are decided.
3. Habitual abode. If the vital interests are balanced, you are resident where you live habitually — the country where you spend more time as a matter of routine, measured over a sensible period rather than one year.
4. Citizenship. If you have a habitual abode in both or neither, you are resident in the country of which you are a citizen.

Someone who is a citizen of both or of neither country, and who cannot be placed by the first three tests, is referred to the competent authorities — the CRA and the IRS — who settle it by mutual agreement. In our experience that stage is rarely reached, because the permanent home and vital interests tests are decided on facts that people can document.

Losing the tie to the US makes you a deemed non-resident of Canada, departure tax included

If the treaty places you in the US while you still have Canadian ties, Canadian law treats you as a deemed non-resident from the date the tie-breaker tips. The consequences are the same as if you had packed up and left: a final return with a departure date, a deemed disposition of most capital property at fair market value, form T1161 listing property over $25,000, and flat Part XIII withholding on Canadian-source income afterwards. Our departure tax guide and the answer on what departure tax is and how much it costs set out the mechanics.

This is not something you can switch off by continuing to file a Canadian return. Once the facts point to the US, Canada's treatment follows the facts, and filing as a resident for years afterwards creates a mess rather than a defence. The domestic-law route to leaving is described in how to become a non-resident of Canada; the treaty route reaches the same destination by a different door.

Winning the tie for Canada has its own price on the US side. A US citizen does not escape the annual 1040 by being resident in Canada, because the treaty's saving clause lets the US tax its citizens as if the treaty did not exist for most purposes. Our dual citizen tax guide covers that position in full.

Form 8833 on the US side, and why we rarely file an NR73

A person who is a US resident under domestic law but claims Canadian residence under the treaty files a US non-resident return, the 1040-NR, and attaches Form 8833, the Treaty-Based Return Position Disclosure. The IRS can charge a penalty of US$1,000 for each failure to disclose. Two cautions come with that filing. A green card holder who claims treaty non-residence can put the green card at risk and, after long enough, can be treated as having given it up for tax purposes. And the FBAR can still be required in a treaty non-resident year, so we check the accounts before assuming it falls away.

On the Canadian side, form NR73, Determination of Residency Status (Leaving Canada), is voluntary. It asks the CRA to rule on your status from a questionnaire, and a form completed without care invites a determination you did not want and cannot easily undo. We generally advise clients to self-assess with proper analysis and file consistently, and to use the NR73 only where a bank or pension administrator insists on it or the facts are genuinely unclear. People arriving from the US face the same questions in reverse, which we cover in our guide to moving to Canada from the US.

How we approach residency files

We treat the tie-breaker as a fact-finding exercise before it is a filing exercise. We build a dated record of homes, family location, employment, accounts and days in each country, run the four tests in order, and write down the conclusion and the evidence behind it. Then we prepare whichever returns the answer calls for — departure-year T1, 1040-NR with Form 8833, or a resident return in one country and nothing in the other — so both tax authorities see one consistent story. That work is quoted as a fixed fee after a discovery call through our cross-border tax services.

Source: CRA — Determining your residency status and IRS — About Form 8833.