Exchange Rates on Cross-Border Returns: Which Rate, Which Date, and the Phantom Gains That Catch Filers

Every cross-border return converts income, deductions, and asset costs from one currency to the other, and the two agencies have different defaults. The CRA generally accepts the Bank of Canada rate on the transaction date, or an annual average for income received evenly through the year. The IRS expects the spot rate on the date of each transaction, and accepts a yearly average for items received evenly. Where they agree, the conversion is mechanical. Where they diverge, and on capital assets and foreign-currency holdings, the currency itself becomes a source of gain or loss that both countries tax.

Key takeaways

• Income items (salary, interest, dividends, pension): the CRA accepts the Bank of Canada annual average rate for amounts received throughout the year, or the transaction-date rate; the IRS accepts the yearly average rate for items received evenly, otherwise the spot rate.
• Capital transactions (purchase and sale of assets): both agencies expect the transaction-date rate for each leg. The Canadian gain uses the CAD cost at the purchase date and CAD proceeds at the sale date; the US gain uses USD at each date.
• Foreign tax credits: convert the foreign tax at the rate when it was paid (or the average rate if paid throughout the year).
• Foreign currency gains on cash and debt: Canada taxes gains on foreign currency (cash, deposits) as capital gains above a $200 annual exemption; the US taxes gains on foreign currency transactions under section 988 as ordinary income, with a $200 per-transaction exemption for personal transactions.
• Repaying a foreign-currency mortgage can produce a taxable gain in the borrower's home currency if the exchange rate moved in the borrower's favour.

Income items

A US citizen in Toronto earning $150,000 CAD reports about $110,000 USD on the 1040 at a 1.36 average rate; the CRA reports the CAD amount directly. A Canadian in Florida receiving $30,000 of RRIF withdrawals reports $30,000 CAD on the NR4 and about $22,000 USD on the 1040. The IRS publishes yearly average rates; the Bank of Canada publishes daily and annual average rates. Using the annual average for income received monthly is accepted by both; using it for a single large payment is not.

Capital transactions

The currency layer on capital gains is the item that produces the most surprises. A Canadian resident who bought a US stock for $100,000 USD at 1.05 (ACB $105,000 CAD) and sells for $120,000 USD at 1.36 (proceeds $163,200 CAD) has a US gain of $20,000 USD and a Canadian gain of $58,200 CAD, roughly $42,800 USD. The Canadian dollar's decline turned a 20% gain into a 55% gain for Canadian purposes. The reverse happens when the Canadian dollar strengthens: a US-dollar gain can be a Canadian-dollar loss.

The same applies to real estate. A Toronto family that bought a Florida condo at par in 2012 and sells at 1.36 in 2026 has a Canadian gain far larger than the US gain, and the US foreign tax credit covers only the US tax on the smaller US gain.

Foreign tax credits

The Canadian foreign tax credit on Form T2209 converts the US tax paid at the rate when paid; the US foreign tax credit on Form 1116 converts the Canadian tax paid at the rate when paid, or the average rate if paid through withholding during the year. A large Canadian balance paid in April is converted at April's rate. Refunds are converted at the rate when received, which can produce a small currency gain or loss on the credit itself under section 905(c).

Foreign currency as an asset

Canada. Foreign currency held as cash or deposits is capital property. Converting US dollars to Canadian dollars, or using US dollars to buy an asset, is a disposition of the currency; the gain or loss is capital, and the first $200 of net gain or loss in a year is ignored. A Canadian who held $200,000 USD in a US account bought at par and converts it at 1.36 has a $72,000 CAD capital gain, $36,000 taxable.

United States. Section 988 treats gains and losses on foreign currency transactions (disposing of foreign currency, repaying foreign-currency debt) as ordinary income or loss. Personal transactions are exempt if the gain is under $200 per transaction. A US resident who holds Canadian dollars and converts them, or who repays a Canadian-dollar mortgage when the Canadian dollar has weakened, has a section 988 gain: the USD value of the debt when borrowed exceeds the USD cost of repaying it.

The mortgage trap

An American who bought a Toronto home with a $600,000 CAD mortgage at 1.25 (USD equivalent $480,000) and repays it at 1.40 (USD cost $429,000) has a $51,000 USD section 988 gain, taxable as ordinary income, on the mortgage payoff, even if the house was sold at a loss. Canada has no equivalent on a Canadian-dollar mortgage held by a Canadian resident, but a Canadian who repays a US-dollar mortgage after the US dollar weakened has a capital gain on the debt.

Worked example

A Vancouver resident holds $300,000 USD in a US brokerage account (bought at 1.10) and $50,000 USD in a US savings account (deposited at 1.10). She sells the portfolio for $360,000 USD at 1.36 and converts the savings to Canadian dollars at 1.36.

• Portfolio. US gain $60,000 USD. Canadian gain: proceeds $489,600 CAD less ACB $330,000 CAD = $159,600 CAD; $79,800 taxable. The currency contributed about $78,000 CAD of the gain.
• Savings. Canadian capital gain on the currency: $68,000 CAD less $55,000 CAD = $13,000 CAD, less the $200 exemption; $6,400 taxable.
• US. The portfolio gain is $60,000 USD at long-term rates (if she files a 1040-NR only for FIRPTA or ECI she does not; portfolio gains of a non-resident are not US-taxable). The savings conversion is not a US event for a non-resident.

Official sources

"Accordingly, amounts expressed in a currency other than the Canadian dollar must be converted to Canadian dollars using the relevant spot rate for the particular day on which the amounts arise, if they are relevant in computing the taxpayer's Canadian tax results. [...] For a particular day after February 28, 2017, the relevant spot rate to be used to convert an amount from one currency to another, where one of the currencies is Canadian currency, is the rate quoted by the Bank of Canada on that day." — Canada Revenue Agency, Income Tax Folio S5-F4-C1, Income Tax Reporting Currency, https://www.canada.ca/en/revenue-agency/services/tax/technical-information/income-tax/income-tax-folios-index/series-5-international-residency/series-5-international-residency-folio-4-foreign-currency/income-tax-folio-s5-f4-c1-income-tax-reporting-currency.html

"You must express the amounts you report on your U.S. tax return in U.S. dollars... Use the exchange rate prevailing when you receive, pay, or accrue the item." — Internal Revenue Service, Foreign Currency and Currency Exchange Rates, https://www.irs.gov/individuals/international-taxpayers/foreign-currency-and-currency-exchange-rates

Practitioner note

Clients track their gains in the currency of the account and are surprised when the Canadian return shows a gain twice as large. We keep the Canadian cost base in Canadian dollars at the purchase-date rate for every foreign asset from the day it is bought, and we warn Americans in Canada about the section 988 gain on paying off a Canadian mortgage after the loonie falls.

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 dual-currency cost base records, the foreign currency gain computations in both countries, and the annual returns with the correct conversions. See cross-border pricing or book a call.