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Borrowing against your house to invest isn't reckless or genius. It's just leverage.

The tax deduction is real. So is the fact that a market drop doesn't shrink what you owe the bank.

A home equity line of credit lets you borrow against the paid-down portion of your house, usually at a lower rate than an unsecured loan, since the house is the collateral. Used to invest the proceeds — rather than to renovate a kitchen or consolidate debt — that borrowing can also become tax-deductible in Canada. Both halves of that sentence are true, and neither one cancels out the other.

The mechanism, without the recycling loop

This is simpler than it sounds, and simpler than its more famous cousin, the Smith Manoeuvre. There's no readvanceable mortgage, no tax-refund-reinvestment cycle, no gradual conversion of your whole mortgage into investment debt. It's one decision, made once or repeated periodically:

1. You have equity in your home — value above what you still owe on the mortgage.
2. A HELOC lets you borrow against that equity, typically up to a combined 80% loan-to-value across the mortgage and HELOC together (the federal guideline that governs how much Canadian lenders can extend), with the HELOC portion itself commonly capped further, around 65% of the home's value.
3. You draw some or all of that available room and invest it in a non-registered account, in something with a genuine, reasonable expectation of producing income.
4. Because the borrowed funds were used to invest, the interest on that draw is deductible under the same Income Tax Act provision that makes the Smith Manoeuvre work — Section 20(1)(c). Your regular mortgage payments continue exactly as before; nothing about them changes.

The Smith Manoeuvre is a specific, systematic version of this same principle — the same interest-deductibility mechanic, applied on a recurring schedule as mortgage principal frees up new HELOC room, aimed at eventually replacing the whole mortgage with deductible debt. What's below applies whether you draw the HELOC once for a lump sum or do it this way repeatedly; if you want the deeper mechanics of the automated version, that's a separate read.

The risk a deduction doesn't touch

Strip away the tax treatment and this is leveraged investing, full stop: you're borrowing money, secured against your home, to put into markets that can go down. If the portfolio drops 30%, the HELOC balance doesn't drop with it — you still owe every dollar, plus interest, regardless of what the investments are currently worth. A few consequences that are easy to underweight in the moment:

• Your home is the collateral, not the portfolio. A margin call on a brokerage loan forces a sale at a specific bad moment; a HELOC doesn't work that way day-to-day, but the debt is still secured against the one asset most households can least afford to lose access to.
• HELOCs are typically demand facilities. Lenders generally have latitude to reduce available credit or adjust terms, particularly if home values fall meaningfully — a risk a fixed-term mortgage simply doesn't carry.
• Fully drawing a HELOC to invest spends the same emergency-liquidity cushion a HELOC often quietly serves as. Money already invested and margined against the house isn't there for a job loss or a roof repair.