Roth Conversions Before a Move to Canada: Why the Window Closes at the Border, and How to Size One

The Roth conversion is one of the few US tax moves that is strictly better done before a move to Canada than after, and the reason is the treaty's mechanics rather than the rates. The treaty protects a Roth IRA held by a Canadian resident through the election the Roth guide describes — Canadian tax on the plan's growth is deferred, and qualified distributions are excluded from Canadian income as they are from US income — but the protection covers only the portion of the Roth that existed, with its growth, before any Canadian contribution; a contribution made while resident in Canada, including a conversion from a traditional IRA, is a Canadian contribution that permanently removes the treaty protection for that slice and its subsequent growth, converting it into an ordinary taxable account for Canadian purposes with the tracking burden of separating protected and unprotected portions. And the conversion itself, if made while a Canadian resident, is taxable in both countries: the US includes the converted amount as ordinary income (as it would for any resident), and Canada includes it as pension income received (a distribution from the traditional IRA, which the treaty allows Canada to tax when the recipient is a Canadian resident), with a foreign tax credit for the US tax — so the conversion bears Canadian rates (higher, at most brackets) rather than US rates, and the Roth that results is tainted for Canadian purposes anyway. Before the move, by contrast, the conversion is a purely US event: taxed by the US at the converter's US bracket, ignored by Canada (a non-resident's US transaction in a US account), and the resulting Roth balance — all of it, including the converted amount — is protected by the treaty election filed with the first Canadian return. The sizing question is the ordinary US one with a cross-border edge: convert in the final US-resident years up to the top of a bracket the converter is comfortable paying — the last US year is often a partial-income year (the job ends mid-year, or the move is early in the year), and a partial-income year has unused lower brackets that make it the cheapest conversion year the converter will ever have; pay the conversion tax from funds outside the IRA (using IRA funds to pay the tax shrinks the Roth and, for those under 59½, triggers the 10% additional tax on the portion withheld); and consider the state — a conversion in a high-tax state is taxed by that state as well, so the converter leaving California should compare converting in the final California year against establishing residence in a no-income-tax state first, where the timeline allows (the state-residency guide covers the break). The comparison the converter is actually making: a traditional IRA carried into Canada is taxed at distribution — by the US at 15% on periodic payments (final, under the treaty) and by Canada at full Canadian rates with the 15% credited — so the Canadian resident's effective rate on traditional IRA withdrawals is their Canadian bracket, often 40-50% at meaningful income; a Roth IRA carried into Canada, with the election, is withdrawn tax-free in both countries. The conversion therefore trades US tax now at the converter's final-US-year bracket (perhaps 22-24% federal for a partial year, plus state) for the avoidance of Canadian tax at 40-50% later — a trade that favors converting far more strongly for a Canada-bound retiree than for a US retiree who expects a similar bracket in retirement. The limits on the case: the converter who expects to return to the US in retirement (the Canadian-rate avoidance evaporates); the converter who needs the IRA funds within five years (the five-year rule on converted amounts, and the Canadian tax on distributions of the tainted or untainted portions); the converter whose final US year is a full-income year in a high bracket (the trade is still positive against Canadian rates but less dramatic); and the converter with a required minimum distribution already running (RMDs cannot be converted, and the RMD must be taken first). The sequence, for someone moving in a given year: in the year before the move, convert to the top of the target bracket; in the move year, before the residency start date (the day Canadian residence begins under the residency tests — the move-date guides), convert again to the top of the bracket the partial year's income leaves available, paying the tax from savings; then cross the border, file the treaty election with the first Canadian return covering the whole Roth, and never contribute or convert again while resident in Canada. The estate and beneficiary note: a Roth carried into Canada passes to beneficiaries under US rules, and the treaty election's protection is analyzed for the beneficiary's own residence — a Canadian-resident beneficiary of a Canadian-resident's Roth generally benefits from the same treatment, while the tainted portion follows its own rules. The mirror case for completeness: the Canadian moving to the US with a Roth conversion in mind has no Canadian Roth to convert (the TFSA is the Canadian analogue, and it is collapsed on the way south per the tax-free-accounts guide); and the American in Canada who wants Roth exposure after the move cannot get it without tainting — the window is the border, and it closes on the residency date.

Key takeaways

• After the move, conversions are taxed twice and taint the Roth: Canada taxes the conversion as pension income at Canadian rates, the US taxes it as ordinary income, and the converted slice loses treaty protection permanently as a Canadian contribution.
• Before the move, a conversion is a US-only event: taxed at the converter's US bracket, ignored by Canada, and fully protected by the treaty election filed with the first Canadian return.
• The final US year is usually the cheapest conversion year: partial-year income leaves lower brackets unused — convert to the top of the comfortable bracket before the residency start date, paying the tax from outside the IRA.
• The trade favors Canada-bound retirees: US tax now at 22-24% federal (partial year) against Canadian rates of 40-50% on traditional IRA withdrawals later — far stronger than the domestic conversion case.
• Watch the state and the limits: high-tax final-year states tax the conversion; returners to the US, five-year-rule cases, full-income final years, and RMD-age converters weaken the case.
• The window closes on the residency date: convert before it, elect after it, never contribute or convert while resident in Canada.

The pre-move conversion plan

Determine the residency start date under the Canadian tests. Project the final US year's income (partial-year salary, other income) and identify the unused bracket room. Model the conversion amount to the top of the target bracket (federal and state), with the tax paid from savings. Compare the US tax now against the Canadian tax avoided on the same amount at projected retirement brackets. Execute the conversion before the residency date. File the treaty election with the first Canadian return. Freeze the Roth. The plan is a spreadsheet and a calendar, and the only unrecoverable error is the conversion dated one day after the residency start.

Worked example

A Seattle physician moving to Vancouver on August 1 holds a US$700,000 traditional IRA and a US$150,000 Roth. Final US year: seven months of salary put her in the 24% bracket with about US$90,000 of room below its top; Washington has no state income tax. The plan: convert US$90,000 in the year before the move (to the top of that year's 24% bracket — about US$21,600 of federal tax paid from savings), and US$90,000 more in the move year before August 1 (about US$21,600 again). Result: US$180,000 moved from traditional to Roth at 24% federal — US$43,200 of tax — with no Canadian tax (non-resident at the time) and no state tax. First Canadian return: the Article XVIII(7) election covering the full US$330,000 Roth. Go-forward: no contributions, no conversions, tax-free growth and withdrawals in both countries. The alternative she was considering — converting after settling in, "once things calm down" — would have taxed the same US$180,000 in Canada as pension income at BC rates near 50% with a 24% US credit (net about 50% total, roughly US$90,000 against her US$43,200), and tainted the converted slice for Canadian purposes forever. Her remaining US$520,000 traditional IRA stays traditional: withdrawn in retirement at 15% US withholding (periodic, creditable) and Canadian rates — the account she couldn't afford to convert at once, converted over the two years the border allowed.

Official sources

The CRA explains that a Canadian resident who holds a Roth IRA may elect under Article XVIII(7) of the treaty to defer Canadian tax on income accrued in the plan, and that contributions made while a Canadian resident are treated as Canadian contributions that affect the election. — Canada Revenue Agency, Income Tax Folio S5-F3-C1, Taxation of a Roth IRA, https://www.canada.ca/en/revenue-agency/services/tax/technical-information/income-tax/income-tax-folios-index/series-5-international-residency/folio-3-cross-border-issues/income-tax-folio-s5-f3-c1-taxation-roth-ira.html

Contributions to a traditional or Roth IRA require "taxable compensation," and compensation does not include "any amounts (other than combat pay) you exclude from income, such as foreign earned income and housing costs." — Internal Revenue Service, Publication 590-A, Contributions to Individual Retirement Arrangements, https://www.irs.gov/publications/p590a

Practitioner note

Roth conversions are the rare move that is cheaper before the border and expensive after it — the treaty election protects only what existed before Canadian residency, and a post-move conversion is taxed at Canadian rates and tainted besides. Our pre-move plan finds the residency date, fills the final US year's unused brackets with conversions paid from savings, and files the election with the first Canadian return; the sequence is simple, and the one-day-late conversion is the mistake we can't undo.

See also: For how the RRSP and the 401(k) compare across the border, see how the RRSP and the 401(k) compare across the border; and browse every cross-border tax topic guide, organized by situation.

Next step

Fairlight prepares the pre-move Roth engagement — residency-date determination, bracket-room modeling for the final US years including state effects, conversion execution before the residency date, the treaty election with the first Canadian return, and the go-forward contribution freeze. See cross-border pricing or book a call.