Pay Off Mortgage Early vs. Invest

The Core Question

You have $500/month extra. Should you put it toward your mortgage principal, or invest it in a diversified portfolio? Both paths have merit, and the right answer depends on your mortgage rate, expected investment returns, tax situation, and risk tolerance.

Let's work through all of it.

The Math: Guaranteed Return vs. Expected Return

Paying extra on your mortgage gives you a guaranteed, risk-free return equal to your mortgage interest rate. If your mortgage rate is 6.5%, every dollar of extra principal payment saves you 6.5% annually in future interest — with zero risk.

Investing gives you an expected return — not a guaranteed one. A diversified equity portfolio (e.g., a broad index fund) has historically returned 7–10% annually before inflation, but with significant year-to-year volatility. In any given year, returns could be -30% or +30%.

A Real Comparison: $500/Month for 10 Years

Based on $500/month, $480,000 mortgage at 6.5%, 22 years remaining. Investment returns are nominal before tax.

At average historical returns, investing comes out ahead in raw dollar terms. But that assumes consistent above-mortgage returns, and doesn't account for tax on investment gains.

The Tax Factor

In Canada, mortgage interest is not tax-deductible for your primary residence (unlike in the US). This simplifies the comparison: your mortgage rate is your true cost of debt, and investment gains in non-registered accounts are subject to capital gains tax.

If you're investing in a TFSA, gains are tax-free — which improves the case for investing. If you're investing in a non-registered account, deduct ~25–30% from your expected return for a like-for-like comparison.

The Risk Factor

When Paying Off the Mortgage Wins

• Your mortgage rate is 6.5% or higher — the guaranteed return is hard to beat after tax
• You're close to retirement and want to eliminate your largest monthly expense
• You have a low risk tolerance and market volatility causes you stress
• You don't have TFSA contribution room (non-registered investing has tax drag)
• You have variable-rate mortgage risk and want to reduce exposure

When Investing Wins

• Your mortgage rate is below 5% and you have TFSA room to invest tax-free
• You're early in your career with decades of compounding ahead
• You have high risk tolerance and won't panic-sell in a market downturn
• You have employer RRSP matching — matched contributions are an instant 50–100% return
• Your emergency fund is strong and you're not stretched financially

The Practical Answer: Do Both

The mathematically optimal answer changes year to year with interest rates and market conditions. The practically optimal answer for most people is a split:

1. Always max employer RRSP matching first — it's an instant 50–100% return, better than any other option
2. Max your TFSA next — tax-free compounding improves investment returns significantly
3. Then split remaining extra cash — some to mortgage principal, some to non-registered investing

This approach gives you the guaranteed benefit of accelerated mortgage payoff while building a diversified investment portfolio. You don't have to pick one.