When Does a Canadian Need to File a US Tax Return?

Canadians file US tax returns for one of four reasons: they hold US citizenship (including accidental Americans who have never lived in the US), they hold a green card, they meet the substantial presence test, or they earned US-source income that is not fully exempt under the treaty. The first three make you a US person, which means you file a 1040 on worldwide income. The fourth means you file a 1040-NR reporting only the US-source income. The filing threshold, the forms, and the penalties are different for each path, and getting the wrong one costs more than getting it right.

Path 1: You are a US citizen

US citizenship creates a lifelong worldwide filing obligation. If you are a US citizen, you file a 1040 every year, reporting income from all sources worldwide, regardless of where you live, where you earn the income, or whether you owe any US tax after credits.

This includes:

• Dual citizens born in the US who moved to Canada as children and have lived there ever since
• Children of US citizens who acquired citizenship at birth under IRS 301(a) even if born in Canada
• Naturalized US citizens who later moved back to Canada
• Accidental Americans who may not have known they were US citizens

The filing threshold for 2025 is $14,600 for single filers and $29,200 for married filing jointly. But the threshold is almost always exceeded for anyone with employment income, so the practical rule is: if you are a US citizen and you have income, you file.

On top of the 1040, US citizens living in Canada also owe:

• FBAR (FinCEN 114) if the aggregate value of foreign accounts exceeds $10,000 at any point
• Form 8938 if foreign financial assets exceed $200,000 year-end ($300,000 max during year) for filers abroad
• Form 3520/3520-A if you hold a TFSA, RESP, or other account the IRS classifies as a foreign trust
• Form 5471 if you own 10% or more of a Canadian corporation
• Form 8621 if you hold Canadian mutual funds or ETFs that are PFICs

The US tax is generally zero or near-zero because Canadian tax rates exceed US rates at most income levels, and the foreign tax credit (Form 1116) offsets the US liability. But the forms are not optional.

Path 2: You hold a green card

A green card holder is a US tax resident for as long as the card is valid, even if they move back to Canada. The filing obligation is identical to a US citizen: worldwide income, Form 1040, same information returns (FBAR, 8938, 5471, 8621, 3520).

The green card test under IRC 7701(b)(1)(A)(i) treats you as a US resident for the entire calendar year in which you hold the card. If you got your green card on November 15, you are a US resident for all of that year (or you file a dual-status return splitting the year at the green card date).

Abandoning the green card. The filing obligation does not end when you stop living in the US. It ends when you formally abandon the card by filing Form I-407 with USCIS or when the card is administratively or judicially revoked. If you held the card for 8 of the last 15 years, you may be a “long-term resident” subject to the exit tax under IRC 877A, the same regime that applies to US citizens who renounce.

Path 3: You meet the substantial presence test

If you are not a US citizen or green card holder but you spend enough days in the US, you become a US tax resident under the substantial presence test. The formula:

Days in the US in the current year, plus one-third of the days in the prior year, plus one-sixth of the days two years prior. If the total is 183 or more, and you were present at least 31 days in the current year, you are a US tax resident.

This catches Canadian snowbirds, cross-border commuters, and anyone who spends significant time in the US. Once you meet the test, you file a 1040 on worldwide income, the same as a citizen or green card holder, for the portion of the year starting from your residency starting date (or the full year if you make an election).

The escape valves:

• The closer connection exception (Form 8840) lets you remain a non-resident even if you meet the 183-day formula, as long as you were present fewer than 183 days in the current year (not the weighted count) and you maintained a closer connection to Canada.
• The treaty tie-breaker can override the substantial presence test if you are a resident of both countries under domestic law, by treating you as a resident of one country for treaty purposes. This requires a Form 8833 disclosure.

Canadian snowbirds who stay under 183 actual days in the current year and file Form 8840 typically do not owe a US return. But if you cross the line, the entire worldwide filing obligation kicks in.

Path 4: You are a non-resident with US-source income

If you are not a US citizen, green card holder, or substantial presence test resident, you may still need a US return if you earned US-source income. Non-resident aliens file Form 1040-NR to report US-source income.

The most common US-source income types for Canadians:

• US employment income. If you worked physically in the US (even for a few days on a business trip), the income allocated to those US workdays is US-source. The treaty exempts short-term business visitors under certain conditions (employer is not a US entity, presence is under 183 days in a 12-month period, and the compensation is not borne by a US permanent establishment), but if the exemption does not apply, you file a 1040-NR.
• US rental income. If you own US rental property, the rental income is US-source. Without a Section 871(d) election, the US withholds 30% of gross rent. With the election, you file a 1040-NR and pay tax on net rental income at graduated rates. Almost every Canadian landlord makes the election.
• Sale of US real property. FIRPTA requires the buyer to withhold 15% of the gross sale price when a non-resident sells US real property. You file a 1040-NR to report the gain (or loss) and recover excess withholding.
• US business income. If your business has a permanent establishment in the US (an office, a place of business, or an agent with authority to conclude contracts), the business profits attributable to that PE are US-source.
• US partnership or S-corp income. If you are a partner in a US partnership or own shares in a US S-corp, your share of income is US-source and you file a 1040-NR.
• US dividends. The US withholds on dividends paid to non-residents (15% treaty rate under Article X). If the withholding fully satisfies the US tax, you generally do not need to file a return. But if you want to claim a lower rate, adjust the withholding, or report additional US income, you file.
• Gambling winnings. The US withholds 30% on casino and lottery winnings paid to non-residents. Canadians can recover this by filing a 1040-NR and claiming the treaty exemption under Article XXII (for specific types of gambling income) or reporting deductible gambling losses.

What if the treaty exempts the income?

The treaty may exempt certain income from US tax (or reduce the withholding rate to zero), but a treaty-based exemption does not always eliminate the filing requirement. If you are taking a treaty position to exclude income that would otherwise be taxable, the IRS requires a Form 8833 disclosure with your return.

• The practical rule: if you are relying on a treaty article to avoid US tax on income that the US would otherwise tax under its domestic law, file the return and attach the 8833. If you skip the return, the IRS does not know you are claiming the exemption, and the statute of limitations on assessment may never start running.

What are the consequences of not filing?

The penalty structure for cross-border non-filing is severe, and the information return penalties are often larger than the tax itself:

• Failure to file (IRC 6651(a)(1)): 5% of the unpaid tax per month, up to 25%.
• FBAR penalty (non-willful): up to $10,000 per account per year. Willful: the greater of $100,000 or 50% of the account balance.
• Form 5471 penalty: $10,000 per form per year, and the statute of limitations on the entire return stays open until the form is filed.
• Form 3520/3520-A penalty: the greater of $10,000 or 5%/35% of the trust value, depending on the violation.
• Form 8938 penalty: $10,000 per failure, plus $10,000 per month after notice, up to $50,000.

For US citizens and green card holders who have never filed from Canada, the Streamlined Foreign Offshore Procedures offer a path to come into compliance without penalties (3 years of returns, 6 years of FBARs, and a non-willfulness certification). For those in the US, the Streamlined Domestic Offshore Procedures require a 5% penalty.

What should I do next?

Start with two facts: your US tax status (citizen, green card, substantial presence, or none of those), and whether you have US-source income. If either one is yes, you likely need a return. The form, the scope, and the information returns depend on which path brought you in.

• Substantial presence test formula, the 183-day weighted calculation
• Form 8840: closer connection exception, the way snowbirds avoid US tax residence
• Dual-status return vs full-year election, filing options for the year you arrive in the US
• Form 1040-NR for Canadian non-residents, the return for US-source income without US residency
• FBAR filing requirements, the $10,000 aggregate threshold
• US citizen in Canada who has never filed, the compliance path
• Accidental American: never filed US taxes, the decision tree for citizens who did not know

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.