Should You Pay Off Debt or Invest? The Math Might Surprise You
It's one of the most common money dilemmas. The answer depends on your interest rate — and there's a clear mathematical line that tells you which move puts more money in your pocket.
Meet the person this article is for
Marcus, 34, Calgary. Has $18,000 on a car loan at 6.9% and $500 extra per month he could either put toward the loan or start investing in his TFSA. His dad says "never have debt." His friend says "always invest early." Who's right?
The Core Principle: Compare Your Rates
Paying off debt is a guaranteed return. If you have a debt at 20% interest and you pay $1,000 toward it, you just "earned" a guaranteed 20% return on that money — because it won't accrue 20% interest next year.
Investing in the stock market has historically returned about 6–8% annually after inflation, but it's not guaranteed. So the question becomes: can you reliably beat your interest rate by investing instead?
Debt rate: Above 8%
Pay debt first
You'd need to beat this in the market consistently. Statistically unlikely.
Debt rate: 5–8%
It depends
Consider your risk tolerance, tax situation, and employer match.
Debt rate: Under 5%
Consider investing
Historically, diversified markets have beaten rates in this range.
Two Situations Where You Should Always Invest First
Your employer matches RRSP contributions
A 50% or 100% employer match is an instant, guaranteed return that no debt payoff strategy can beat. If your employer matches $1 for every $2 you contribute, that's a 50% return before your money even grows. Always capture the full match first — it's free money.
Your debt has a very low interest rate (under 3–4%)
Some mortgages or student loans locked in at very low rates make it mathematically attractive to invest the difference. The historical equity premium has consistently beaten these rates over long periods.
Your Personal Payoff vs. Invest Comparison
Adjust the sliders to model your own situation and see which strategy builds more net worth over 10 years.
Common debt types:
Investing first wins
After 10 years: Pay debt first → $49,259 net worth vs. Invest first → $72,034 net worth
Difference: $22,775 in favour of investing
Net worth = investments minus remaining debt. Assumes minimum payments cover interest on "invest first" scenario.
The Middle Ground: Do Both
The math says to maximize whichever has the better "return" — but psychology matters too. Many Canadians do best with a split approach: put 60% toward debt and 40% toward investing. You make progress on both fronts, reduce debt stress, and still benefit from compound growth.
Marcus's actual plan (from our persona):
Result: Debt gone by year 4, then serious wealth-building from years 4–10. The hybrid approach removed the mental burden of "all debt, no progress" while still growing investments.
What About the Mortgage?
The mortgage question is the most nuanced. At today's rates (around 4–6%), it's genuinely a toss-up. Here's how most financial planners think about it:
Maximize your TFSA first — withdrawals from your TFSA don't affect OAS/GIS eligibility in retirement like RRSP withdrawals do.
If you have an RRSP deduction room and earn over $70K, an RRSP contribution might give a bigger immediate tax benefit than extra mortgage payments.
If the mortgage stresses you out and affects your sleep, peace of mind has real value. It's okay to prioritize emotional security alongside math.
Use your prepayment privilege — most mortgages let you pay 10–20% of the original balance as a lump sum per year. A $1,000 lump sum early in the mortgage can save $3,000+ in interest over the amortization.
Key Takeaway
The simple rule: if your debt rate is higher than your expected investment return, pay the debt first. Credit card debt at 20%? Pay it aggressively — no investment reliably beats that. Mortgage at 4.5%? The case for investing is strong. Either way, capture any employer RRSP match before doing anything else — it's an instant 50–100% return you can't afford to leave behind.
Model your debt payoff and investment growth together