State Income Tax for Cross-Border Workers: The Layer the Treaty Doesn't Reach

The Canada-US treaty binds the federal governments. US states are not parties to it, and most do not follow it. A Canadian whose wages are exempt from federal tax under Article XV can still owe New York tax on the days worked in Manhattan; a Canadian whose RRSP growth is deferred federally owes California tax on it annually; a Canadian who works remotely from Toronto for a New York employer can be taxed by New York under a rule the treaty has nothing to say about. The state layer has its own residency tests, its own sourcing rules, and its own view of the treaty, which is usually to ignore it.

Key takeaways

• States are not bound by the treaty. Federal treaty exemptions (Article XV on wages, Article XVIII on RRSPs, Article VII on business profits) do not automatically apply at the state level. Some states conform because they start from federal AGI (which already reflects the treaty); others, and any state with its own definitions, do not.
• Non-resident wages: every state with an income tax taxes non-residents on wages for days worked in the state, subject to state-specific thresholds (some tax from the first day; a few have day or dollar thresholds).
• Convenience of the employer: New York, Connecticut, Delaware, Nebraska, Pennsylvania, and (for New York-based employers) New Jersey treat a non-resident employee of an in-state employer who works remotely for their own convenience as working in the state. A Canadian in Toronto working remotely for a New York company can owe New York tax on all wages.
• Residency: states have their own residency tests (domicile, and statutory residency at 183 days plus a permanent place of abode in New York, California's facts-and-circumstances test), applied independently of the federal substantial presence test and the treaty tie-breaker.
• RRSP: California taxes the growth annually; most other states follow federal deferral because they start from federal AGI; New York and a few others have unsettled positions.
• Reciprocity: some neighbouring states agree to tax wages only in the state of residence (DC, Maryland, Virginia; Illinois with several neighbours; Pennsylvania with several), which simplifies commuters within the US but has no Canada-US equivalent.

Non-resident wages

A Canadian who works in a US state is taxed by that state on wages for the days worked there, at the state's non-resident rates, regardless of the federal Article XV exemption. New York taxes from the first day (with a 14-day exception for certain occasional presence); California from the first day; Illinois after 30 days; Arizona after 60 days; and so on. The employer withholds state tax on those days and issues a state W-2; the Canadian files a non-resident state return. Canada allows a foreign tax credit for the state tax (the CRA treats state income tax as a creditable foreign tax), so the state tax is recovered against Canadian tax on the same wages.

The federal exemption, claimed on Form 8233, does not bind the state; some states accept the federal position administratively (a state that starts its computation from federal AGI excludes exempt wages automatically), but states like New York, which compute non-resident tax on state-source wages directly, do not.

The convenience rule

Under New York's rule, a non-resident employee of a New York employer who works from outside New York is treated as working in New York on those days unless the remote work is required by the employer (a bona fide employer office at the remote location, or the employer's necessity). A Canadian in Toronto working remotely for a Manhattan firm because the firm allows remote work has New York-source wages for every day under this rule. New York's position has been upheld in state courts; the treaty offers no relief because New York is not a party. The Canadian resident pays New York tax and claims a Canadian foreign tax credit, so the cost is the excess of New York's rate over the credit's usefulness, plus the compliance.

Connecticut applies the rule only to residents of states that apply it to Connecticut residents; Pennsylvania, Delaware, and Nebraska apply versions of it; New Jersey applies it to employees of New Jersey employers who live in states with a convenience rule.

State residency

A Canadian who spends substantial time in a US state can become a state resident under the state's rules even while remaining a Canadian resident under the treaty. New York's statutory residency test: 183 days in the state plus a permanent place of abode (a condo, an apartment available year-round). California's test: presence for other than a temporary or transitory purpose, with a nine-month presumption. State residency means state tax on worldwide income, with no treaty override and, in most states, no credit for Canadian tax.

The federal treaty tie-breaker that assigns a dual resident to Canada does not assign them for state purposes. A snowbird with a New York apartment who spends 190 days there is a New York statutory resident regardless of Form 8840.

The RRSP

States that start from federal AGI or federal taxable income (most of them) inherit the federal treaty deferral: RRSP growth is not in federal AGI, so it is not in state income. California starts from federal AGI but specifically disregards treaties and taxes RRSP earnings annually. New York's position is unsettled; Massachusetts and Pennsylvania have their own income definitions and their treatment should be documented. No-income-tax states have no issue.

Reciprocity and credits

States give a credit for tax paid to other states on the same income (a resident of one state working in another). Most states give no credit for foreign tax, including Canadian tax: a California resident with Canadian rental income pays California tax on it with no credit for the Canadian tax. Canada, by contrast, gives a foreign tax credit for state tax. The asymmetry means state tax is usually a net cost to a Canadian resident (recovered through the Canadian credit) but Canadian tax is a pure double cost to a US state resident.

Worked example

A Toronto financial analyst works for a Manhattan firm: 90 days a year in the New York office, the rest remotely from Toronto. Salary $200,000 USD.

• Federal. 90 US workdays; $75,000 of US-source wages; over $10,000 and the employer is US-resident, so Article XV's 183-day rule does not apply; US federal tax on the $75,000 on a 1040-NR; the remaining $125,000 is not US-source federally.
• New York. The 90 days are New York-source. Under the convenience rule, the remote days from Toronto are also New York-source (remote work by the employee's choice for a New York employer): New York taxes all $200,000 as non-resident wages.
• Canada. All $200,000 taxed as a resident; foreign tax credit for the US federal tax on $75,000 and the New York tax on $200,000, limited to the Canadian tax on the US-source portion.
• Net. New York's tax on the remote days is creditable in Canada only to the extent Canada considers the income US-source, which for the remote days it does not (the work was performed in Canada). The New York tax on the $125,000 of remote wages is likely a double cost.
• Fix. The employer designates the Toronto home as a bona fide employer office (difficult), or the analyst spends the remote days at the firm's Toronto affiliate under a local employment arrangement.

Official sources

New York State explains that a nonresident employee of a New York employer who works from a location outside New York for the employee's own convenience is treated as working in New York for the days worked outside the state. — New York State Department of Taxation and Finance, TSB-M-06(5)I, New York Tax Treatment of Nonresidents and Part-Year Residents Application of the Convenience of the Employer Test, https://www.tax.ny.gov/pdf/memos/income/m06_5i.pdf

"You will be considered a United States resident for tax purposes if you meet the substantial presence test for the calendar year. To meet this test, you must be physically present in the United States (U.S.) on at least: 31 days during the current year, and 183 days during the 3-year period that includes the current year and the 2 years immediately before that." — Internal Revenue Service, Substantial Presence Test, https://www.irs.gov/individuals/international-taxpayers/substantial-presence-test

Practitioner note

The state is the taxing authority that Canadian clients forget and the treaty cannot help with. New York's convenience rule is the worst case: a Toronto remote employee of a Manhattan firm can owe New York tax on days spent in Toronto, and Canada will not credit it. We map the state before the employment contract is signed, and we structure the remote arrangement so the days in Canada are not New York days.

See also: Planning a move? Start with the Canada-to-US tax checklist and browse every corridor by city, province, and state.

Next step

Fairlight prepares the state residency and sourcing analysis, the non-resident state returns, and the Canadian foreign tax credit for state tax. See cross-border pricing or book a call.