What it means
The mechanism depends on separating two uses of money, because borrowing to buy a home for personal use is different from borrowing to earn taxable investment income. Canadian interest-deduction rules examine the use of borrowed funds, not simply the property pledged as security.
A readvanceable mortgage combines a mortgage with a home-equity credit line, and as principal is repaid, available borrowing capacity can increase under the lender's terms. The borrower then uses newly drawn credit for qualifying investments rather than household spending.
Repaying and redrawing equal amounts can leave total principal debt unchanged at that point, but the composition changes to less personal mortgage debt and more investment debt, and interest, fees, further borrowing or capitalised costs can change the total, so the strategy is not automatically debt reduction. CRA's interest-deductibility folio describes conditions including a legal obligation to pay interest and borrowed money used for an eligible income-earning purpose, and the deduction is also subject to limits such as reasonableness.
Tracing is central: the taxpayer must link borrowed money to an identifiable eligible use, and current use can matter when investments are sold or funds are redirected. Separate accounts and clear transfer records can make this easier to demonstrate.
An investment does not qualify merely because its price might rise, since CRA distinguishes an income-earning purpose from a reasonable expectation of capital gains alone. Rules for registered or tax-exempt investments also require separate attention; ordinary assumptions about taxable investment borrowing should not be carried into those accounts.
A deductible expense remains an expense, so if eligible interest reduces taxable income, the tax saving covers only part of the interest at the taxpayer's effective marginal rate. The strategy also introduces investment risk secured indirectly by home equity: markets can fall while the credit line remains payable, so a homeowner can have a smaller investment portfolio without a matching reduction in debt.
Interest-rate risk can compound the problem, because a variable-rate credit line can become more expensive while investment income stays flat or falls. Model the ability to service debt without relying on hoped-for capital appreciation or tax refunds arriving immediately.
A tax refund may be used to repay mortgage principal, allowing further investment borrowing if the lender permits, but the refund reflects the actual tax position, not guaranteed cash. Unlike a general cash-out refinance, this strategy links ongoing principal repayment and reborrowing to an investment purpose and Canadian tax analysis.
Before starting, the homeowner needs advice covering lending terms, taxation, cash flow and investment suitability, and outside Canada local law may produce a different result even when a similar loan structure is available.
In practice
Real-world examples.
Example
A fictional homeowner repays $1,000 of mortgage principal and redraws $1,000 to a separate investment account. The transaction converts part of the borrowing's use, but total principal debt has not fallen from those two movements alone. Keeping the redrawn money in its own account makes the later tracing straightforward.
Example
A fictional investor redraws home-equity credit to pay for a holiday. The home's security does not make interest on that personal spending deductible as investment borrowing. The investor should keep that borrowing separate from any investment credit line.
Example
A fictional homeowner sells an investment and uses the proceeds for household expenses. The current use and tracing position need review before continuing to claim interest deductions. A tax adviser confirms what portion of the borrowing still has an eligible use.
Formula
Calculation
Illustrative after-tax interest cost = eligible interest x (1 - marginal tax rate). For a $50,000 investment borrowing balance at an assumed 7% annual rate, interest is $50,000 x 0.07 = $3,500. If the full amount qualifies and the relevant marginal rate is 40%, the tax saving is $3,500 x 0.40 = $1,400 and the after-tax interest cost is $3,500 - $1,400 = $2,100, before fees.
A build-up example: repaying and redrawing $1,000 a month for 12 months moves $12,000 from mortgage debt to investment debt. Interest on $12,000 at 7% is $840, the tax saving at 40% is $336, and the after-tax cost is $504 for the year, again assuming the full amount qualifies and ignoring fees and the gradual build-up of the balance.
A deduction cannot prevent investment losses or make a negative return profitable by itself.Case study
Seen in the real world.
This case study is fictional and illustrative. A Canadian homeowner considers the strategy after seeing an example showing a smaller personal mortgage balance. Her adviser asks her to model combined mortgage and investment debt, not just the first account. A higher-rate scenario reveals that investment distributions would not cover interest. She also sees that a market decline could reduce the portfolio while the borrowing remains outstanding.
The lender's credit limits and the family's cash reserve constrain how far the plan can proceed. She chooses a smaller initial amount and keeps the borrowing and investment records separate. The tax adviser reviews eligible use and filing treatment. The decision is based on an affordable risk exposure, not the misleading idea that the home loan itself has acquired a blanket deduction.
Watch out
Common mistakes.
- Claiming the original personal mortgage interest becomes deductible without an eligible borrowing use.
- Treating a partial tax saving as elimination of interest cost or investment risk.
- Mixing personal spending and investment transfers without records that trace the borrowed money.
Questions
People also ask.
Is total debt automatically reduced?
No. Equal principal repayment and reborrowing change the composition of debt, not its total at that point.
Does every investment qualify?
No. Income-earning purpose, account type and current use matter under Canadian tax rules.
Is the strategy risk-free?
No. Borrowing costs, investment losses and home-equity exposure remain even if some interest is deductible.
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