Double taxation is two countries taxing the same income, in the same year, in the hands of the same person: the country where the income arises taxes it first, and the country where the taxpayer lives (or, for Americans, holds citizenship) taxes it again. Most of that second bill disappears through one of three relief mechanisms: a credit for the foreign tax paid, an exemption of the foreign income, or a deduction of the foreign tax from taxable income.
For a US or Canadian foreign-property owner, the foreign tax credit does nearly all of the work, the exemption method matters mainly for Americans earning wages abroad, and the deduction is a fallback worth pennies on the dollar. Your total burden on cross-border income lands at roughly the higher of the two countries’ rates, not the sum. The money leaks through the gaps: taxes that are not income taxes (property tax, transfer tax, VAT), income taxed in different years by each country, and foreign rates the home country will not fully credit.
Juridical vs economic double taxation
The OECD Model Tax Convention, the template behind most of the world’s bilateral treaties, defines international juridical double taxation as the imposition of comparable taxes in two or more states on the same taxpayer, on the same income, for the same period.[OECD Model Tax Convention on Income and on Capital, Introduction, 2026-07] One person, one income stream, two tax bills: a Canadian resident paying tax on Lisbon rent in both Portugal and Canada is the textbook case.
Economic double taxation is different: the same income taxed twice in the hands of two different taxpayers. The classic pattern is a corporation taxed on its profits and its shareholder taxed again on the dividend paid from them. For property buyers it shows up when a foreign company holds the real estate: the company pays local tax on rental profit, and the owner pays home-country tax when the profit comes out. Canadians who hold property through a foreign corporation walk into this structure, plus a reporting regime on top; see holding foreign property through a corporation.
Treaties are built to fix the juridical kind. If the same dollar is taxed in two hands rather than one, no treaty article guarantees a fix.
Residence vs source: when the two claims collide
Source taxation is the source country’s claim: income arising inside its borders is taxable there, whoever earns it. Rental income from a Spanish apartment is Spanish-source; a gain on selling a Mexican condo is Mexican-source. Under virtually every treaty, income and gains from real property stay taxable in the country where the property sits, so a foreign-property owner is permanently on the source side of the ledger and cannot treaty-shop out of it.
Residence taxation is the home country’s claim: residents are taxable on worldwide income, wherever earned. Canada taxes on residence, determined by factual ties (home, spouse, dependants) plus a deeming rule: sojourn in Canada 183 days or more in a year and you are resident for the whole year.[CRA Income Tax Folio S5-F1-C1, Determining an Individual's Residence Status, 2026-07]
The United States goes further: it taxes citizens and green-card holders on worldwide income no matter where they live.[IRS Publication 54, Tax Guide for U.S. Citizens and Resident Aliens Abroad, 2026-07] An American who moves to Canada is taxed by Canada as a resident and by the US as a citizen, on everything, every year. US treaties preserve this through a savings clause, so the treaty reduces the collision but does not remove it; the full citizenship-based regime, disclosure forms included, is mapped in US citizens taxed abroad.
Treaties referee the overlap. A treaty assigns taxing rights item by item, caps withholding on dividends and interest, and in its elimination-of-double-taxation article (Article XXIV in the Canada-US treaty) obliges the residence country to relieve what remains, usually by credit. The article-by-article machinery is mapped in how tax treaties work. The US publishes its full treaty network on the IRS treaties A to Z page;[IRS, United States Income Tax Treaties A to Z, 2026-07] Canada’s Department of Finance list covers more than 90 countries in force.[Department of Finance Canada, Tax Treaties, 2026-07]
Hold income-producing property abroad and both countries assess the same income; whether you feel it twice depends on which relief mechanism applies and how well it works on your numbers.
Mechanism 1: the foreign tax credit
The credit method is the North American default. The residence country calculates its own tax on the foreign income, then subtracts the income tax already paid to the source country, dollar for dollar, up to a ceiling: the home tax attributable to that foreign income. You pay the source country in full and the home country only the excess, if its rate is higher.
A worked example. A Canadian resident nets CAD 10,000 of rental income from a Portuguese apartment and pays CAD 2,500 of Portuguese income tax on it. At a 40% combined federal-provincial marginal rate, the Canadian tax on that income is CAD 4,000. The foreign tax credit under section 126 of the Income Tax Act wipes out CAD 2,500 of it, leaving CAD 1,500 payable to the CRA.[Income Tax Act, section 126, Foreign Tax Credit, 2026-07] Total burden: CAD 4,000, exactly what a Canadian-source landlord at the same rate would pay.
On the US side the mechanism runs through Form 1116, capped at US tax times the ratio of foreign-source to total taxable income and computed separately by income category, with unused credits carried back one year and forward ten.[IRS Publication 514, Foreign Tax Credit for Individuals, 2026-07] The baskets, the limitation math, and a worked Lisbon-rental example are in the Form 1116 foreign tax credit guide.
Strengths. The credit preserves progressivity, applies to earned and unearned income alike, and requires no treaty: both countries grant it unilaterally.
Limits. Three bite regularly. The credit covers income taxes only; property and transfer taxes never qualify. It is non-refundable, so foreign tax above the home-country ceiling is stranded. And the two systems treat the stranded excess differently: the US carries it back one year and forward ten, while Canada’s non-business credit (rental income and capital gains, for most individual owners) has no carryover at all, leaving only the subsection 20(11) and 20(12) salvage deductions.[CRA Income Tax Folio S5-F2-C1, Foreign Tax Credit, 2026-07]
Mechanism 2: exemption
Under the exemption method the residence country does not tax the foreign income. Many European treaties use exemption-with-progression, where the exempt income still pushes the taxpayer’s other income into higher brackets. Neither the US nor Canada uses it as a general method, which is why the credit dominates here. One large US exemption still matters.
The foreign earned income exclusion lets a US citizen or resident who lives abroad (bona fide residence or 330 days of physical presence in a 12-month window) exclude foreign wages and self-employment earnings from US tax entirely: up to $130,000 for 2025 and $132,900 for 2026, elected on Form 2555.[IRS, Foreign Earned Income Exclusion, 2026-07]
The catch: the exclusion covers earned income only. Rental income, capital gains, dividends, interest, pensions: none of it qualifies, so the FEIE is close to irrelevant for property income. The full credit-versus-exclusion decision, including the stacking rule and the five-year revocation lockout, is worked through in the Form 1116 guide. Canada has no general equivalent for individuals; the nearest thing a property owner will meet is the principal residence exemption on foreign property, which can shelter the gain on a foreign home.
Mechanism 3: the deduction
The weakest relief: you subtract the foreign tax from taxable income rather than from your tax bill, so each dollar of foreign tax is worth only your marginal rate.
A worked example. A US filer in the 32% bracket pays $5,000 of foreign income tax. As a credit it is worth $5,000; as an itemized deduction it reduces US tax by $1,600. The credit wins by more than three to one, and for foreign income taxes the US makes it an annual either-or choice: credit all or deduct all, not a mix.
The deduction exists for the cases where the credit strands. For a Canadian that means the subsection 20(11) and 20(12) salvage rules, worked through dollar by dollar on the Canadian foreign tax credit page. A US filer whose Form 1116 ceiling is zero (no net foreign-source income after allocations) gets nothing from a credit but still gets marginal-rate value from deducting.
Verdict. Take the credit unless it is arithmetically worthless. The deduction is salvage, not strategy.
The three mechanisms side by side
| Credit | Exemption | Deduction | |
|---|---|---|---|
| What it does | Subtracts foreign tax from home tax | Removes foreign income from the home tax base | Subtracts foreign tax from taxable income |
| Value of $1 of foreign tax | $1, up to the home-tax ceiling | n/a (income never taxed at home) | Your marginal rate, roughly $0.25 to $0.45 |
| Main US instance | Form 1116 foreign tax credit | Foreign earned income exclusion, Form 2555 | Itemized deduction for foreign income taxes |
| Main Canadian instance | Section 126 credit, per country | No general equivalent | Subsections 20(11) and 20(12) |
| Covers property income | Yes | No, earned income only (US) | Yes |
| Unused amounts | US: 1 back, 10 forward; Canada: business tax only | n/a | n/a, reduces income in the year taken |
| Fails when | Foreign rate exceeds home rate, or tax is not an income tax | Income is unearned | Almost always second-best |
Where relief fails
Total double taxation is rare. Partial double taxation is common, and it clusters in four places.
Taxes that are not income taxes
The credit and deduction systems relieve income taxes. Annual property taxes (Mexico’s predial, Spain’s IBI), acquisition and transfer taxes, notary and registry charges, and VAT on new construction are not income taxes, so no foreign tax credit ever offsets them. At best a purchase-side tax joins the property’s cost base and shrinks a future gain. US itemizers lost the deduction for foreign real property taxes in the 2018 federal tax changes, and current law keeps them out of the state-and-local deduction.[IRS, Instructions for Schedule A (Form 1040), Taxes You Paid, 2026-07] The country pages price these unrelieved costs: Mexican taxes for American buyers and Spanish taxes for Canadian buyers.
Rate differentials and stranded credits
When the source country’s effective rate on an income stream exceeds the home country’s rate, the excess forfeits. An American can park it in the carryover and hope for a fatter foreign-income year within the decade; a Canadian with excess non-business foreign tax has only the deduction salvage described above. High-withholding jurisdictions without a treaty are where this bites hardest.
Timing mismatches
The credit assumes both countries tax the income in the same period. They frequently do not. The sharpest property example is Canadian emigration: ceasing Canadian residency triggers a deemed disposition that taxes accrued gains immediately, while the new country and the property’s country tax the real sale years later. Tax paid now and tax paid in year five do not line up in any single year’s credit calculation, and part of the gain can be taxed twice across the two events. The mechanics and elections are in departure tax and foreign property. Milder versions come from mismatched tax years, foreign assessments issued years after the home return, and FX movements between accrual and payment.
Taxes the other country will not credit
The US net investment income tax is the live example: a 3.8% surtax on investment income that sits outside the regular income-tax chapter, which the IRS says the statutory foreign tax credit cannot offset. Americans resident in Canada have challenged that position, and the Court of Federal Claims agreed in December 2024 that the Canada-US treaty supports a treaty-based credit against the NIIT; the government’s appeal was argued at the Federal Circuit in March 2026, and a decision is pending.[Bruyea v. United States, 174 Fed. Cl. 238 (Ct. Fed. Cl. Dec. 2024), 2026-07] Until the appeals resolve, an American in Canada with substantial investment income carries unrelieved double tax on that 3.8%.
FAQ
Is double taxation illegal? No. No rule of international law prevents two countries from taxing the same income; treaties and credits exist because the overlap is lawful.
Do tax treaties eliminate double taxation completely? They come close on juridical double taxation of income, chiefly by guaranteeing the credit. They do little for the economic kind, nothing for non-income taxes, and cannot cure timing mismatches between tax years.
Credit or deduction, which should a filer take? The credit, in almost every case: it offsets tax dollar for dollar while the deduction returns only the marginal rate. The deduction earns its keep where the credit is stranded.
Does owning a foreign home by itself cause double taxation? Not on income. Annual property taxes are a carrying cost, not double taxation. The income-tax overlap starts when the property produces rent or is sold at a gain; for Canadians the disclosure obligations can start on day one.
Where to go next
Start at the taxes hub for the full map. Canadians reporting a foreign property should read T1135 foreign property reporting for the disclosure side and CRA rules on foreign rental income for how the credit runs through a real rental return. Anyone planning a permanent move should price the deemed-disposition timing problem in departure tax and foreign property before, not after, giving up residency.