Should You Pay Off Your Mortgage or Invest?
The forums are split on this. Overpay or invest, pick a side, fight in the comments. Both camps miss the same number, and once you've seen it your answer is obvious.
When each strategy almost always wins
| Your situation | Overpay wins | Invest wins | Why |
|---|---|---|---|
| Mortgage rate above 5 to 6% | Yes | - | Risk-free return beats expected portfolio return |
| Mortgage rate below 3% | - | Yes | Long-run equity returns clear the bar with room to spare |
| ISA and pension already filled | Yes | - | Post-tax GIA return often dips below mortgage rate |
| Higher-rate taxpayer with pension headroom | - | Yes | 40% relief and NI savings beat any mortgage rate |
| Within 5 to 10 years of retirement | Yes | - | Cuts fixed costs before income drops |
Most UK households do best with a deliberate blend, not one strategy exclusively.
Key takeaways
Overpaying your mortgage gives a guaranteed, risk-free return equal to your mortgage interest rate.
Investing has historically delivered higher returns, but those returns are not guaranteed and come with volatility.
The breakeven point is the investment return you need just to match the benefit of overpaying - anything below that and you would have been better off reducing the mortgage.
For most people, the right answer is a blend: clear high-rate debt first, then split spare cash between overpayments and investing in an ISA.