Debt Payoff vs Investing: The Comparison That Is Actually Fair
This article is the comparison for unsecured and other non-mortgage debt, plus the two exceptions that survive it. The residence mortgage is a different species: lower rate, a contract privilege, a penalty if you guess wrong, and interest that is not deductible. The hurdle arithmetic for that loan is prepayment versus investing. The order among the mortgage, the TFSA, and the RRSP is which dollar first. Use those pages for the house. Do not paste their stack onto a credit card and call it a strategy.
Every debt gets its contractual minimum so you are not in default while you optimize. The minimum on a revolving balance is how the balance survives. The decision in this article is what happens to the next dollar after the minimums, not whether to pay them.
The comparison, with the tax written on both sides
On debt whose interest you cannot deduct, the return from a prepayment is the interest rate itself. You do not pay tax on interest you no longer owe. There is no market path where that return goes negative. That is the hurdle.
On debt whose interest is deductible because the borrowed money earns income, the hurdle is lower. An illustrative rate of 6 percent at an illustrative 40 percent marginal rate is an after-tax cost of 3.6 percent. Those figures are a picture of the formula — rate times one minus your marginal rate — not a quote and not your bracket. Find the bracket in the federal and provincial guides, then use the rate on your own agreement. Deductibility is a use test. A line of credit that bought a television does not become deductible because a different part of the same line bought units. The tracing file is the CRA-clean HELOC guide. This page will not rebuild it.
On the investment side, write down an expected return you can defend, then take tax off if the account is non-registered. A TFSA return is after tax already. An RRSP return is not a gift: the deduction arrives now and the inclusion arrives later, which is the RRSP playbook, not a reason to carry a card balance. A diversified equity portfolio's long-run expectation is an assumption. It is not a rate a bank owes you. If you cannot say the assumption out loud after imagining a large drawdown, you do not have an expected return.
A revolving balance at 20 percent, non-deductible, requires a pre-tax return above 20 percent in a taxable account just to tie, before behaviour. No sober equity assumption clears that. A personal loan at an illustrative 9 percent, non-deductible, still clears most people's after-tax GIC and many people's honest equity assumption once you haircut for the chance of quitting. A deductible investment loan at an illustrative 6 percent and a 40 percent marginal rate hurdle of 3.6 percent can lose to a TFSA equity holding in expectation — and that expectation can be negative for years. The loan still has to be serviced from cash flow. If it cannot, the expectation is irrelevant.
Punitive debt is not a debate
Revolving unsecured debt priced in the high teens or higher is a math problem with one answer. Pay it. Do not dollar-cost-average into a TFSA while a card compounds. Do not keep the balance because a points plan rebates one or two percent. The rebate is not in the same units as the interest. The earn rate on a card you revolve is a distraction; the stack, if you pay in full, is the stack templates.
Payday-style borrowing and deferred-payment plans that become high-rate debt after a promo are the same species. Read the rate that applies when the promo ends. If you cannot pay the balance before that date from money already in the cash-flow system, you are not financing a purchase. You are taking a loan.
Two exceptions that are easy to fake
- An employer match, on the matched slice only. A dollar-for-dollar match, or any match you can read in the plan text, is an immediate return on the contributed dollar. Confirm the formula and the cap. Declining that slice to pay a moderate-rate debt is refusing compensation. The exception ends at the cap. Dollars above the match go back into the hurdle comparison. A match does not justify carrying a punitive card. Pay the card, and take the match, and cut spending until both fit. If they cannot both fit this month, the card is the emergency.
- RRSP room at a genuinely higher marginal rate, with the refund assigned in advance to the debt or the TFSA. The refund loop is already worked in which dollar first. Use it for moderate-rate debt and for the mortgage. Do not use it to narrate a 20 percent card. A deduction does not outrun interest in the high teens, and a refund that gets spent was not part of the plan.
The spreadsheet assumes the invested dollar stays invested. If the household spends surplus that was "going to be invested," the hurdle was never cleared, because the investment never happened. Automate the winner. A debt payment that is a bill will occur. A TFSA transfer that waits for motivation often will not. The automation stack is the enforcement. The saving-rate target is the amount you automate, not the amount you announce.
The mortgage is a different species
Principal-residence interest is generally not deductible. The rate is usually far below unsecured revolving debt, the prepayment privilege is capped, and breaking a term to "get ahead" can cost a penalty that wipes out the hurdle. Some households hold a cheap term they should not rush to repay. Some hold a rate that beats any safe investment they would actually buy. Both statements can be true of different contracts in the same year. Read your commitment. Then use the hurdle guide and the account order. An FHSA for a home you have not bought yet is not a prepayment problem. It is sequencing.
Borrowing to invest, including a Smith Manoeuvre, is not "investing instead of paying debt." It is adding debt. Interest deductibility, leverage, and the risk of a forced unwind live in the Smith Manoeuvre guide. Do not import that structure into a decision about a credit-card balance.
An order that stays out of the mortgage article's way
- Pay every contractual minimum.
- If a card or other punitive balance exists, direct the surplus there until it is gone. Keep a small cash buffer so the next repair does not reopen it. The buffer is the emergency-fund guide.
- Take the employer match up to the cap, unless step 2 makes that impossible this month. If it is impossible, the budget is the emergency, not the match math.
- For what remains — moderate personal loans, a deductible investment loan you can service, a mortgage — run the after-tax hurdle, then place the investment dollar with the account guides rather than with a new theory.
Statement APRs, promo end dates, and mortgage coupons are on documents you already have. A blog's "typical" rate is not your hurdle. If the rate is variable, rerun the comparison when it resets, not when a market headline makes you restless.
Key takeaways
- Non-deductible interest is a risk-free after-tax return equal to the rate. The investment has to beat it after tax and after behaviour.
- High-teens revolving debt is not a close call. Pay it before you fund a portfolio.
- A match is an exception on the matched dollars only. An RRSP deduction is an exception when the refund is assigned and the rate is moderate.
- Deductible interest uses a lower hurdle, and only if the use test is clean.
- The mortgage decision is already written. Use the prepayment guides. Do not copy them onto a card.
Related reading
- Mortgage prepayment versus investing — the hurdle for the residence.
- Prepayment versus TFSA and RRSP — the order, including the refund loop.
- CRA-clean HELOC strategies — when interest is deductible.
- Cash-flow system — where the extra payment sits on payday.
- RRSP playbook — the deduction that is not a reason to revolve.
The hurdle is after tax. The bracket is a return entry.
Deductible interest, RRSP refunds, and the marginal rate you think you are in are tax. The 2026 tax guide is that side of the comparison.
Get the 2026 Tax Guide — $49 CAD
