Dual taxation happens when two countries claim tax on the same income in the same year: the country where the income arises taxes it first, and your home country taxes it again as part of worldwide income. Three mechanisms unwind the overlap: a foreign tax credit that offsets home tax with tax already paid abroad, an exemption that removes the income from home taxation, and a deduction that treats foreign tax as an expense. Tax treaties sit above all three, deciding which country gets first claim and capping what the source country can take.
When double taxation actually happens
Canada taxes its residents on worldwide income, whatever the source country already took.[Income Tax Act, section 2, tax payable by persons resident in Canada, 2026-07] The United States goes further: it taxes citizens and green-card holders on worldwide income no matter where they live, which is why an American in Lisbon still files a full US return.[IRS Publication 54, Tax Guide for US Citizens and Resident Aliens Abroad, 2026-07] Real property income is taxed first where the property sits. Both claims are legitimate under each country’s own law. That is the collision.
For a property owner the overlap shows up in three places. Rental income gets taxed at the source (Mexico’s SAT, Spain’s Agencia Tributaria) and again at home on the T1 or Form 1040. A capital gain on sale gets the same double claim. And a buyer who crosses the new country’s tax-residency line, commonly 183 days, becomes a tax resident of two countries at once, both claiming worldwide income until a treaty tie-breaker settles it. Day counts are covered in tax residency rules for Canada and the US.
The three relief mechanisms
| Mechanism | How it works | Canada | United States |
|---|---|---|---|
| Foreign tax credit | Home country reduces its own tax, dollar for dollar, by tax paid at source, capped at the home-country tax on that income | Section 126; CRA folio S5-F2-C1 | Form 1116; IRS Publication 514 |
| Exemption | Home country gives up its claim on the income category entirely | Rare for individuals; mostly treaty-specific carve-outs | Foreign earned income exclusion only, which never covers rental income or property gains |
| Deduction | Foreign tax is deducted from income as an expense, recovering only a fraction of it | Subsections 20(11) and 20(12) | Itemized deduction in place of the credit |
The credit is the workhorse and the right default for property income. It is also capped: if Spain takes more tax on your Valencia rental than Canada would have charged, the excess is not refunded. The US lets unused credit carry back one year and forward ten;[IRS Publication 514, Foreign Tax Credit for Individuals, 2026-07] Canada’s non-business foreign tax credit has no carryforward, and what the credit cannot absorb, a section 20(12) deduction only partly recovers.[CRA Income Tax Folio S5-F2-C1, Foreign Tax Credit, 2026-07] The deduction method is a last resort for foreign tax that fails the credit’s eligibility tests. How the three mechanisms trade off is in double taxation explained; the worked credit math lives on the per-country pages, Canada’s section 126 credit and the US Form 1116 credit.
Where treaties fit
A treaty does not eliminate tax on foreign property; it orders it. Treaties on the OECD pattern give the country where the property sits the first right to tax income from it (Article 6, income from immovable property), cap withholding on dividends and interest, break dual-residency ties, and set up a mutual agreement procedure when the two tax authorities disagree. The home country then grants relief for what the source country kept. That is the summary; the article-by-article mechanics, from Article 6 through the mutual agreement procedure, are in how tax treaties work.
Two catches. First, US treaties carry a saving clause that preserves the US right to tax its own citizens as if most of the treaty did not exist, so a treaty helps a US citizen less than the headline suggests.[Convention Between Canada and the United States of America with Respect to Taxes on Income and on Capital, Article XXIX(2), 2026-07] Second, claiming a treaty position on a US return generally requires disclosure on Form 8833. The Canada-US treaty, the one most readers here will touch, gets its own article: how the Canada-US tax treaty works for individuals.
Coverage across the eight markets this site tracks is uneven:
| Country | Income tax treaty with Canada | Income tax treaty with the US |
|---|---|---|
| Mexico | Yes | Yes |
| Spain | Yes | Yes |
| Portugal | Yes | Yes |
| Italy | Yes | Yes |
| Costa Rica | No, information-exchange agreement only | No |
| Panama | No, information-exchange agreement only | No |
| Belize | No | No |
| Dominican Republic | Yes, in force since 1977 | No |
No treaty does not mean double tax. Canada and the US both grant their foreign tax credits unilaterally, so a Canadian buying in Costa Rica still credits Costa Rican tax against the Canadian bill. What the no-treaty buyer loses is the tie-breaker for dual residency, capped withholding rates, and estate-tax coordination. The full accounting of that gap, market by market, is in countries with no tax treaty.
The tax library
Treaty layer
- Double taxation explained: the credit, exemption, and deduction math, and when each one wins.
- How tax treaties work: the OECD Model article by article, the US saving clause, Form 8833, and where treaty protection stops.
- Canada US tax treaty for individuals: withholding rates, tie-breakers, pensions, and the estate tax credit in Article XXIX-B.
- Countries with no tax treaty: what buyers in Costa Rica, Panama, and Belize lose without one, and what still works.
- Tax residency rules for Canada and the US: residential ties, the substantial presence test, Form 8840, and the 183-day lines.
Mechanics by income type
- Form 1116 foreign tax credit: baskets, the limitation formula, carryovers, and when the FEIE beats the credit.
- Canada’s foreign tax credit: the T2209 lesser-of formula, why non-business credits die each year, and the 20(11) and 20(12) fallbacks.
- Capital gains on selling foreign property: situs rules, FX basis math, and the two-country bill on sale.
- Foreign rental income taxed twice: withholding, net elections, and how the double claim on rent unwinds.
- Cross-border estate tax: US situs assets, Canada’s deemed disposition at death, and Article XXIX-B relief.
- Totalization agreements: how Social Security and CPP coverage and credits combine.
The Canadian filing layer
- Buying property abroad as a Canadian: the umbrella page for the Canadian series.
- T1135 foreign property reporting: the CAD 100,000 disclosure threshold and its penalty stack.
- CRA rules for foreign rental income: reporting the rental on the T1 and crediting the source-country tax.
- Departure tax on foreign property: the deemed disposition when you cease Canadian residency.
- Principal residence exemption on foreign property: when the foreign home can shelter the gain.
- Cross-border estate planning: what happens to the foreign property at death.
- TFSA, RRSP, and foreign property: why registered accounts and foreign real estate barely interact.
- Holding foreign property through a corporation: where the corporate wrapper helps and where CRA punishes it.
The American filing layer
- US citizenship-based taxation abroad: the umbrella page for Americans, centralizing the FBAR and Form 8938 disclosure mechanics, the PFIC trap, and the section 877A exit tax.
The Form 1116 credit mechanics are in Form 1116 foreign tax credit, and each country’s American-buyer tax page carries the source-country detail.
Country tax pages
Four of the treaty markets have their own treaty breakdowns: Mexico, Spain, Portugal, and Italy. Each covers what the US and Canadian instruments do for property owners in that country.
Rates, closing taxes, and the buyer-side filing detail live here, split by passport:
| Country | Canadian buyers | American buyers |
|---|---|---|
| Mexico | Taxes for Canadian buyers | Taxes for American buyers |
| Spain | Taxes for Canadian buyers | Taxes for American buyers |
| Portugal | Taxes for Canadian buyers | Taxes for American buyers |
| Italy | Taxes for Canadian buyers | Taxes for American buyers |
| Costa Rica | Taxes for Canadian buyers | Taxes for American buyers |
| Panama | Taxes for Canadian buyers | Taxes for American buyers |
| Belize | Taxes for Canadian buyers | Taxes for American buyers |
| Dominican Republic | Taxes for Canadian buyers | Taxes for American buyers |
FAQ
Does a tax treaty mean I won’t be taxed twice?
No. The treaty orders the two claims; the foreign tax credit does the relief work. You pay the source country first and your home country tops up to its own rate. For US citizens the saving clause blunts treaty benefits further.
Can I be a tax resident of two countries at the same time?
Yes, and it is common in the first year of a move. Where a treaty exists, its tie-breaker rules (permanent home, centre of vital interests, habitual abode, nationality) assign one residence for treaty purposes. Where no treaty exists, as with Canada and Costa Rica, both claims stand and only the credit mechanisms limit the damage.
Is there any relief when no treaty exists?
Yes. The Canadian and US foreign tax credits are unilateral; they apply to Costa Rican, Panamanian, and Belizean tax the same way as Spanish tax. The credit caps still apply, and the no-treaty gaps (tie-breakers, withholding caps, estate coordination) remain open.
Which mechanism applies to rental income on a foreign property?
The foreign tax credit. The exemption method rarely reaches rental income for Canadians or Americans, and the deduction method recovers only a fraction of what the credit would.
Where to start
A Canadian buyer’s path: tax residency rules first, then double taxation explained, then Canada’s foreign tax credit for the T2209 math, then the T1135 and the rest of the Canadian filing layer, then your target country’s taxes-canadian-buyers page. An American buyer’s path: US citizenship-based taxation abroad for the filings that follow the passport, then double taxation explained, the Canada-US treaty article if you have Canadian ties, then your target country’s taxes-american-buyers page.