Pay Off Debt or Invest? The Actual Break-Even Numbers

"It depends" is one of the most overused phrases in personal finance. Yes, there are variables: tax shelters, employer matching, risk tolerance. But the core math is not mysterious. It's arithmetic. Pay off debt or invest: whichever produces the higher guaranteed or expected return wins.

The problem is that most people never actually run the comparison with their specific numbers. They read "high-interest debt first, then invest" and assume that means credit cards only. Or they hear "always max your 401k" and carry a 22% APR balance for years. Both are wrong in different ways.

This article walks through the real math for every debt type, with specific break-even thresholds and 10-year projections you can compare against your own situation.

The Framework: One Number You Need to Know

The question isn't "should I pay debt or invest?" The question is: which produces a higher effective annual return?

Paying off debt produces a guaranteed return equal to your interest rate. Pay off a 21% credit card and you've earned a guaranteed 21% on that money, with zero risk. No investment does that.

Investing produces an expected return, not a guaranteed one. The S&P 500 has averaged roughly 10% annually over long periods, but the real number that matters for comparison is your after-tax return. In a taxable account, investment gains are subject to capital gains tax. In tax-sheltered accounts (RRSP, TFSA, 401k, Roth IRA), gains compound untouched.

So the comparison is:

• Debt rate (guaranteed return from payoff) vs.
• After-tax investment return (expected return from investing)

The break-even threshold shifts based on where your investments live. More on that shortly.

The Rate-by-Rate Breakdown

Here's every common debt type matched against a 7% gross investment return at a 33% marginal rate. The "after-tax spread" is the gap between your debt cost and your expected net investment gain.

The "annual gap per $10K" column shows what each strategy costs you in real dollars over one year per $10,000 of debt. At 21% credit card debt, carrying $10,000 while investing instead costs you $1,630 per year in net economic loss.

Case 1: Credit Card Debt (19–25% APR)

Credit card debt compounds monthly at rates that erase investing gains completely. Take a $12,000 credit card balance at 22% APR. At a $300/month minimum payment, you'll pay $9,248 in interest over 5.8 years before it's gone.

If instead you invested that $300/month at 7% gross (4.7% after tax) for 5.8 years, you'd accumulate roughly $23,800, but you'd still carry the $12,000 balance plus the $9,248 in interest. You'd be $2,448 behind net versus just paying it off.

The math gets worse the longer you wait. Every month of delay is interest that compounds against you.

Case 2: Mid-Range Debt (7–15% APR)

Personal loans typically run 10–18% APR. Car loans in Canada and the US currently average 7–9%. Even at the lower end of this range, the math tilts toward payoff.

At 9% debt cost versus 4.7% after-tax return, you're losing 4.3 percentage points annually on every dollar invested instead of paid down. On a $20,000 car loan, that's $860/year in avoidable economic loss, every year until the loan is gone.

The counterargument you'll hear: "But you might earn more than 7% on your investments." That's true some years. It's also false in others. The debt rate is guaranteed. The investment return is not. When you're choosing between a certain loss and an uncertain gain, the risk-adjusted math favours debt payoff consistently.

Case 3: Low-Rate Mortgage (<5% APR)

This is the debt most people get backwards. They feel uncomfortable with the mortgage and throw extra cash at it, while leaving RRSP or 401k contribution room untouched.

If you have a $350,000 mortgage at 3.25% and $30,000 in unused TFSA room, the math is clear: putting money into the TFSA captures expected returns of 7% annually, while mortgage prepayment earns only 3.25%. The gap is 3.75 percentage points, or $1,125/year per $30,000, before compounding.

Over 20 years, that difference compounds substantially. This is why the financial advice to "be debt-free" can actually cost low-rate mortgage holders tens of thousands in foregone returns.

The Employer Match Exception: Non-Negotiable

There is one rule that overrides almost everything else: always capture the full employer match before paying extra debt.

Here's why. An employer that matches 100% of your 401k/RRSP contributions up to 4% of salary gives you an immediate 100% return on every dollar contributed. That's before any investment gains. A credit card at 22% APR doesn't come close.

At a $60,000 salary with a 100% match up to 4%, contributing $2,400/year earns $2,400 in employer contributions immediately. That $2,400 is now invested and grows tax-sheltered. No debt payoff produces a guaranteed 100% return.

The only case where skipping the match makes sense: if your financial situation is so destabilized by debt (missed payments, collection calls, creditors threatening legal action) that the psychological and practical harm of the debt outweighs the mathematical benefit of the match. In that case, get stable first.

Otherwise: minimum payments on all debt, full employer match captured, then redirect everything to highest-rate debt first.

10-Year Projection: The Numbers That Settle It

Enough theory. Here's what each approach actually produces over a decade. Scenario: $15,000 credit card debt at 21% APR, $300/month current minimum payment, $400/month extra to allocate. Freed payments are reinvested at 4.7% after-tax once debt is gone.

At 21% APR, paying debt first wins on every metric — not just net position, but portfolio value too. Early debt freedom unlocks $700/month for investing 93 months earlier, which compounds past the gains from starting investments immediately at a 4.7% after-tax rate. The minimum-payment approach ends up with a portfolio nearly $17,000 smaller and $16,750 worse net.

The split feels balanced but sits in a losing middle: slower debt payoff than Strategy A, a smaller portfolio than Strategy A, and a net position $8,250 behind. The math consistently rewards speed on high-rate debt.

Your Specific Decision: Run the Numbers

The framework above gives you the general answer. Your specific situation depends on:

• Your exact debt rate — the number on your statement, not a rounded estimate
• Your marginal tax rate — what you pay on the next dollar you earn
• Whether you have tax-sheltered room — TFSA, RRSP, Roth IRA, 401k contribution space
• Employer matching — and exactly how much you're leaving on the table
• Your investment horizon — longer time horizons shift the balance toward investing

The debt-vs-invest calculator on Unburden takes your exact numbers and produces a clear verdict — including the after-tax comparison, employer match analysis, and a 10-year projection for both scenarios.

Frequently Asked Questions

At what interest rate should you pay off debt instead of investing?

The break-even rate depends on your after-tax investment return. In a taxable account at a 33% marginal rate, a 7% gross market return becomes roughly 4.7% after tax — so any debt above 4.7% mathematically favours payoff. In a tax-sheltered account (TFSA, Roth, 401k), the full 7% return is preserved, so the break-even rises: debt below 7% could lose to tax-sheltered investing.

Should I pay off my credit card or invest?

Pay the credit card. At 19–25% APR, no diversified investment consistently returns more — especially on a risk-adjusted basis. Paying off a 21% card is a guaranteed 21% return. The S&P 500 has averaged roughly 10% gross over long periods, which is less than half that rate. The math is not close.

Should I pay off my mortgage or invest?

For most mortgages originated at 2–4.5% (common from 2020–2023), investing typically wins — especially in tax-sheltered accounts. For 2024 mortgages at 6–7%+, the comparison is much closer. At 6%, the math sits near the break-even line for taxable investing and slightly below it for sheltered accounts. Run the specific numbers for your rate.

Is it always worth capturing employer matching before paying debt?

Almost always. A 50–100% employer match is an immediate guaranteed return that no debt payoff can match mathematically. Even 25% credit card debt loses to a 100% employer match — the match doubles your contribution before any market return is applied. Exceptions exist only when debt-driven financial instability makes stabilizing the highest priority.