Overpay the mortgage or invest?
The great kitchen-table debate, computed honestly: the same monthly amount either shortens your mortgage (a guaranteed saving at your mortgage rate) or goes into investments (a higher but uncertain expected return). Teal is the investment pot; grey is the interest you'd save by overpaying instead.
Your numbers
The same money, two futures
Both lines run to your current mortgage end date. The honest comparison isn't just the bigger number: the overpayment saving is guaranteed; the investment outcome is not, and can be negative. Illustration only — not advice.
Assumptions and method
- Overpaying: the extra is paid monthly on top of the standard repayment for your balance, rate and term; interest saved and the earlier finish date come from simulating the loan month by month. Check your deal's overpayment allowance — many fixes cap penalty-free overpayments around 10% a year.
- Investing: the same monthly amount compounds at your assumed rate. Use a net-of-charges rate, remember tax wrappers (ISAs, pensions — pension tax relief can tilt this comparison heavily), and that markets can fall.
- Not modelled: your mortgage rate changing at refix, the psychological value of being debt-free, or liquidity — investments can be sold in a crisis, mortgage overpayments usually can't be taken back.
Related reading: mortgages explained, investing basics, and what to do with an inheritance for the lump-sum version of this question.
Reminder: this tool is general education, not a personal recommendation — the right answer depends on rates, tax, temperament and circumstances it can't see. For a decision, consult an FCA-authorised adviser; our toolkit shows how to find one.