Orthodontist cross-border tax: the extra US chapter a specialty adds

Why orthodontists so often have a thicker US file than general dentists

Canada has a limited number of orthodontic residency seats, so a meaningful share of Canadian dentists who go on to specialize complete that two- or three-year residency at a US university — on top of a dental degree that may itself have been earned in Canada or the US. That stacking is the reason so many orthodontists arrive at their first DPC consultation with two rounds of US-dollar debt, a short US work history, and retirement or brokerage accounts opened while they were a US resident for tax purposes.

The year you resettle in Canada is the one where each of those threads is cheapest to untangle. Canada treats most property as newly acquired at fair market value on the date you become a resident, so investment gains that built up during your US years generally escape Canadian tax entirely. On the US side, your departure year is typically a dual-status return — resident for the months you were still there, non-resident after — and for most people it is the last 1040-series filing required, unless a green card keeps worldwide US filing obligations alive until it is formally surrendered.

The 401(k) or IRA from a residency-era job

Orthodontic residents and instructors are often paid enough during training to have opened a retirement account, and the choice on what to do with it afterward follows the same three paths as any returning US-trained professional.

The 60(j) transfer requires the balance to reflect services performed while you were not yet a Canadian resident, and the RRSP deposit must land in the year of withdrawal or within 60 days after. Roth accounts are excluded from that route entirely; the usual answer there is a one-time treaty election filed with your first resident-year return, with no further contributions from Canada. See what happens to a 401(k) or IRA when you move to Canada for the general mechanics.

US student debt on top of a dental-school loan

Canada gives no tax relief for interest on US student loans — the federal credit applies only to loans under Canadian government student-aid programs — so neither a dental-school nor a residency-era US loan earns anything on your T1, and the DPC cannot simply assume a debt that funded your personal education. Where residency debt sits on top of dental-school debt, the combined US-dollar payment is often the single largest fixed personal outflow in the early years of practice, which is exactly why we size DPC compensation around it deliberately rather than leaving it to whatever's left after the corporation's own bills are paid.

US continuing education and the occasional lecture fee

Orthodontic continuing education runs heavily through US conferences and study clubs, and course fees that maintain or upgrade your clinical skills remain deductible practice expenses on ordinary principles, with convention travel fitting within the Income Tax Act's two-conventions-per-year limit. A paid lecture or a case-review consulting fee earned on a US trip is different: under the treaty's business-profits article, a Canadian orthodontist with no fixed US base owes no US federal tax on it, but the exemption has to be claimed rather than assumed. Form 8233 switches off the default 30% withholding before payment, and a 1040-NR with Form 8833 documents the position afterward — and state income tax does not always follow the federal treaty, so we check the state before the honorarium is accepted.

Paying a US aligner supplier is a currency question, not a withholding one

Many clear-aligner systems are manufactured and invoiced from the US, which means a recurring USD cost line rather than a US tax exposure: buying a manufactured appliance from a US supplier is a purchase of goods, not a payment for services performed in Canada, so it does not trigger Regulation 105 withholding the way hiring a US contractor to work in your office would. What it does create is exchange-rate exposure on a cost that scales with your case volume, tracked the same way as any other USD supplier account — see orthodontist bookkeeping for how that reconciliation runs. The one scenario worth flagging separately is a US technician or consultant physically providing services inside your Ontario office, which is a different, and much less common, situation from ordering appliances by mail.

Source: CRA — Form T1135, Foreign Income Verification Statement.