Your mortgage interest isn't deductible — but it could be converting.
The Smith Manoeuvre re-borrows every dollar of principal you pay and invests it, turning non-deductible mortgage interest into deductible investment borrowing — with each year's refund recycled into the mortgage. Simulated month by month with the guardrails in plain sight, including the return you'd need just to break even.
Your setup
Semi-annual compounding, the Canadian convention.
Readvanceable lines typically price at prime + 0.50%.
Tax & investing
Combined federal + provincial rate on your next dollar. Most Smith Manoeuvre candidates sit between 35% and 50%.
Long-run annual return on the invested borrowings, before tax on growth.
Prepaying is the classic accelerator — each refund shrinks the mortgage, frees more room, and is re-borrowed to invest.
Cash damming module
Net worth — Smith Manoeuvre vs plain mortgage (identical out-of-pocket cash)
Both scenarios spend exactly the same cash each month; after either mortgage is paid off, the freed payment is invested. Home value appears in both lines equally, so the gap between the lines is the strategy's true effect.
Year 1 — what actually happens
- Monthly mortgage payment
- $2,458
- First month's principal → readvanced and invested
- $973
- Investment-loan balance, end of year 1
- $12,259
- Deductible interest claimed (year 1)
- $271
- Tax refund at 40% — prepays the mortgage
- $109
- Portfolio value, end of year 1
- $12,309
The line's interest is capitalized — borrowed back from the line, the classic cash-flow-neutral structure — and stays deductible when the borrowing is for income-producing investments.
Guardrails — shown, not hidden
- Return needed just to break even
- 2.93%
- If the HELOC rate rises 1%
- advantage becomes $242,314
- Deductibility requires
- Income-producing, non-registered investments
- Not for you if
- Variable income, thin buffer, or you'd sell in a downturn
This strategy is leverage: the investments can fall while the loan doesn't. Portfolio growth is modelled before tax on distributions or gains; real-world taxes on the portfolio reduce the advantage. Deductibility depends on CRA rules (Income Tax Folio S3-F6-C1) and on clean account structure — we set this up with your accountant, not around them. Requires a readvanceable mortgage (combined limit modelled at 80% of home value, revolving portion capped at 65% per OSFI B-20). Simulation, not advice.
- Compares against a plain mortgage spending IDENTICAL out-of-pocket cash — most Smith Manoeuvre illustrations quietly ignore the strategy's cash costs and overstate the win
- Models the classic cash-flow-neutral structure: the line's interest is capitalized (borrowed back), which stays deductible under s. 20(1)(d) — and respects both real credit limits (80% combined, 65% revolving per OSFI B-20)
- Includes a cash damming module for rental and business income — the accelerated conversion most calculators don't even mention
- Tells you the return you'd need just to break even, what a 1% HELOC rate rise costs, and says plainly when your assumptions LOSE money — leverage cuts both ways
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What is the Smith Manoeuvre?+
A Canadian strategy built on a readvanceable mortgage: as each payment pays down principal, the same amount is re-borrowed from the attached credit line and invested in income-producing assets. Mortgage interest on your home was never tax-deductible in Canada — but interest on money borrowed to invest generally is. Over time the same total debt converts from non-deductible to deductible, and each year's tax refund can prepay the mortgage to speed the conversion up.
Is it legal? Does CRA allow it?+
Borrowing to invest in income-producing, non-registered investments is an established, legal basis for deducting interest — CRA's rules are set out in Income Tax Folio S3-F6-C1. What matters is clean execution: the borrowed money must be traceable to eligible investments, which is why we insist on a segregated sub-account and on setting the structure up with your accountant, not around them.
What is cash damming?+
A version for rental or business owners: gross rental/business income goes against your home mortgage as prepayment, while the matching deductible expenses are paid from the readvanceable line. Every routed dollar converts non-deductible mortgage into deductible borrowing immediately — much faster than waiting on regular principal paydown. On a typical file it can cut years off the conversion.
What are the real risks?+
It's leverage. The investments can fall while the loan doesn't, the HELOC rate floats with prime, and the tax benefit only works at your marginal rate. Our simulator shows the break-even return and what a 1% HELOC rate rise does to the outcome — and if your assumptions produce a loss, it says so instead of pretending. It's the wrong strategy for variable income, thin buffers, or anyone who'd sell in a downturn.
Do I need a special mortgage for this?+
Yes — a readvanceable mortgage, where the credit line's limit grows automatically as principal is paid: RBC Homeline, Scotiabank STEP, BMO ReadiLine, TD FlexLine, Manulife One, National Bank All-In-One and several others. The revolving portion is capped at 65% of home value under OSFI's B-20 guideline (80% combined). Setting the right one up — with the sub-account structure the deduction depends on — is exactly the placement work we do.
Does the strategy cost anything each month?+
Structured classically, no — the line's interest is capitalized (borrowed from the line itself), which keeps it cash-flow neutral, and interest on money borrowed to pay deductible interest is itself deductible under s. 20(1)(d) of the Income Tax Act. Our simulation models exactly that structure, and compares it against a plain mortgage spending identical out-of-pocket cash.
Related: Manulife One simulator → · How we work with accountants → · Prepayment privileges calculator →