Overpay the mortgage or save
Type your mortgage, a monthly amount and a savings rate. It compares overpaying with saving the same money over the years you choose, with tax on the savings interest unless it's in an ISA.
Illustration · returns aren't guaranteed and can go down · figures checked 23 Oct 2026 · guidance, not advice · sources
Good to know
- Rates stay where you type them, and tax uses the 2026 to 2027 rates for every year.
- Many lenders let you overpay a set amount each year, often 10% of the balance, before an early repayment charge applies. Your mortgage terms give the limit.
Questions
Which is better?
It depends on the rates, your tax and what else you need the money for. Savings can be reached in an emergency; overpayments usually can't.
How is tax on savings worked out?
Interest over your Personal Savings Allowance is taxed at your rate. The allowance is £1,000 at basic rate, £500 at higher rate and none at additional rate. Interest in an ISA isn't taxed.
Where the figures come from
The rates in force, checked 23 October 2026:
- Tax on savings interest and the Personal Savings Allowance
- ISAs: £20,000 a year, no tax on the interest
Related tools
See both in one place
The Net Worth Tracker Spreadsheet shows your mortgage and your savings side by side, month by month.
Net Worth Tracker Spreadsheet · £7.79 on Etsy