The Smith Maneuver Explained: Turning Your Mortgage Into an Investment Portfolio

The maneuver needs a readvanceable mortgage: a mortgage and a line of credit (a HELOC) registered together against your home, where every dollar of principal you repay on the mortgage becomes a dollar you can borrow on the line. Most large Canadian lenders offer one.

Take a household with a $400,000 mortgage at 4.5% over 25 years, a line of credit at 5%, and a 40% marginal tax rate. These are round illustrative numbers, and every example below uses them. The mortgage payment is $2,223 a month.

In month one, $1,500 of that payment is interest and $723 repays principal. Under the maneuver they immediately borrow that $723 from the line of credit and buy, say, a broad dividend-paying ETF in a taxable account. Nothing else changes: same payment, same house.

Over the first year the payments repay $8,861 of principal, and all of it is re-borrowed and invested. Because the line starts at zero, its interest in year one is small: $201, which brings a refund of $81 the following spring. At the end of the year they owe $391,139 on the mortgage and $8,861 on the line.

Add those two together: still $400,000. That is the most important fact about the Smith Maneuver. Your total debt does not go down while you do it. The mix changes from non-deductible to deductible, and in exchange you own a portfolio.

Keep going and the refunds grow with the line of credit, and every one of them is prepaid onto the mortgage. That is what speeds the plan up: in our example the mortgage is gone after 21 years and 8 months instead of 25 years. By then the household has paid $167,162 of interest on the line and received $61,708 back in refunds.

From that month on they owe $400,000 on the line of credit, all of it deductible, against a portfolio built from every dollar they ever repaid. They keep owing it until they sell investments to repay it: the maneuver does not make the debt disappear, it moves it.

The fair question is not whether the portfolio grows. It is whether the household ends up better off than if it had simply paid down its mortgage. So we compared it with an ordinary household that has the same mortgage and spends exactly the same every month: instead of paying interest on a line of credit, it invests those same dollars in the same portfolio. We stop the clock when the Smith household's mortgage is gone and count what each household owns minus what it still owes.

The dividing line is the after-tax cost of the borrowing. At 5% interest and a 40% tax rate, each borrowed dollar costs 3.0% a year after the refund (5% times 0.60), and our model breaks even almost exactly there, at a return of 3.0% a year. Below that, the maneuver loses to simply paying off the mortgage: at 2% a year the Smith household finishes $32,122 behind. Above it, the gap widens fast because the whole $400,000 is invested: at 8% a year it finishes $241,523 ahead.

Leverage works in both directions. At year 15, on the 5% path, the household owes $213,767 on the line and the portfolio is worth $297,141. Now give it the fall the S&P 500 took in the 2008 financial crisis: 56.5% in price from peak to trough in our crash study. The portfolio drops to $129,334. The debt does not drop at all, so they now owe $84,432 more than their investments are worth. A fall like the 2020 COVID crash (34.1%) would leave the portfolio at $195,802, still $17,965 short of the debt.

Rates can move at the same time. Our model holds the line at 5%, but real lines of credit float. Canada's prime rate went from 2.45% in early 2022 to 7.20% by mid-2023. On a line priced at prime plus 0.5%, the interest on that $213,767 balance would have gone from about $6,306 a year to about $16,460 ($3,784 to $9,876 after the refund), paid from the same household budget.

One real advantage over borrowing from a broker: a line of credit secured by your home does not issue margin calls when the portfolio falls, so no one forces you to sell at the bottom. But the lender can typically reduce or freeze the limit, and the interest is due every month whatever the market does. Selling in a panic turns a paper loss into a permanent one, and the debt is still there afterwards.

Most explanations stop at the tax. The investing decisions matter as much:

The basic maneuver has a few common variants, each with its own trade-off:

The maneuver is not a free lunch. It is borrowing to invest with a tax deduction attached, and the examples above show where that tends to work and where it tends to hurt:

The model here uses a steady return, and markets never deliver one. Before borrowing against your home, backtest the exact mix you would buy, replay it through 2008, 2020 and 2022 in the stress test, and run Monte Carlo ranges to see how often a long stretch looks like the weak path. If the drop you see would make you sell, the maneuver is not for you, whatever the tax math says.

Education, not tax, legal or investment advice. Tax rules change, and the CRA's guidance on interest deductibility (Income Tax Folio S3-F6-C1) is the place to check the current position.