Why U.S. Citizens in Canada Pay More Tax on Investment Income Than They Think

A portfolio of Canadian dividend stocks, properly structured, can produce annual income with an after-tax yield that leaves most fixed-income investors envious. The math changes completely if the investor is a U.S. citizen. The same portfolio, held by someone with a U.S. passport, can trigger a permanent tax leak that no amount of cross-border planning fully closes.

The United States and Eritrea are the only two countries that tax citizens on worldwide income regardless of where they live. A U.S. citizen who has lived in Toronto for twenty years, works for a Canadian employer, and holds only Canadian investments still files an annual IRS return. The Canada-U.S. Tax Treaty provides Foreign Tax Credits to prevent double taxation, but those credits are not a dollar-for-dollar offset. They work when the two countries tax the same income at roughly the same rate. They fail when the rates diverge or when the countries categorize the income differently.

Where the Treaty Breaks Down

Canadian dividend income is the clearest example. Canada taxes dividends from Canadian corporations at a lower effective rate than ordinary income, achieved through the Dividend Tax Credit. The credit is designed to integrate corporate and personal taxes so the combined burden stays roughly neutral. The IRS does not recognize that credit. It taxes the dividend as ordinary income, applies the U.S. marginal rate, and allows a foreign tax credit only for the tax Canada actually collected. If Canada collected less because of the Dividend Tax Credit, the shortfall becomes U.S. tax owing.

A similar problem surfaces with capital gains. Canada includes half the gain in taxable income. The U.S. includes the full gain but taxes it at a lower rate. When you work through the arithmetic with real numbers, the Foreign Tax Credit often leaves a gap. The gap widens if the gain occurred partly because the Canadian dollar strengthened against the U.S. dollar. The IRS measures gains in USD. A stock that lost value in Canadian terms can still produce a taxable gain in U.S. terms if the exchange rate moved the right direction.

The 3.8% Surcharge Nobody Sees Coming

The Net Investment Income Tax adds 3.8% to investment income for U.S. taxpayers whose modified adjusted gross income exceeds $200,000 (single) or $250,000 (married). The tax applies to dividends, interest, and capital gains. In 2021, the U.S. Tax Court ruled in Toulouse v. Commissioner that foreign tax credits cannot be used to offset the NIIT. That makes the 3.8% a permanent cost, layered on top of whatever Canada already collected.

For a high-income U.S. citizen in Ontario, where the combined marginal rate on eligible dividends is roughly 39%, adding 3.8% pushes the effective rate above 42%. That is higher than the rate a Canadian citizen pays on the same income, and higher than most U.S. citizens expect when they see the treaty described as preventing double taxation.

The TFSA Trap

Tax-Free Savings Accounts are treated by the IRS as ordinary taxable accounts. Income earned inside a TFSA is reportable on the U.S. return every year. Gains are taxed as they accrue. The account that Canadian residents use as the centerpiece of tax-efficient investing becomes one of the least efficient vehicles available to a U.S. citizen living in Canada.

RRSPs are protected under the treaty as tax-deferred retirement accounts, which makes them the safest place for U.S. citizens to hold investments in Canada. That leaves taxable accounts and TFSAs as the danger zones, and most cross-border tax risk sits in those two buckets.

The standard advice for Canadians is to hold Canadian equities in taxable accounts and U.S. equities in registered accounts. For U.S. citizens, that advice reverses or vanishes entirely, depending on what the portfolio holds and where the income comes from. The effective rate often lands higher than either country's published schedule would predict.