Key facts: Most fixed-rate mortgages allow penalty-free overpayments of 10% of the balance per year (some lenders 20%, some unlimited on trackers/SVR). Beyond the allowance, early repayment charges of 1–5% apply. Overpayments reduce capital immediately, and choosing to keep payments level and shorten the term saves the most interest.
Your overpayment allowance
The standard deal allows 10% of the outstanding balance per calendar or product year — on a £200,000 balance, £20,000 of headroom annually, which comfortably absorbs most people's spare cash. The details vary by lender: how the 10% is measured, whether unused allowance rolls over (usually not), and how lump sums versus monthly extras are treated. Check yours before making a large payment; an avoidable ERC wipes out years of benefit.
Reduce the term, not the payment
When you overpay, lenders offer two treatments: lower your future monthly payment, or keep it level and shorten the term. Shortening the term is where the big savings live — you compress the years over which interest accrues. Regular modest overpayments made early in a mortgage's life do disproportionate work, because early-years balances are highest. Our guide to paying off your mortgage early runs the strategies side by side.
Overpay or save instead?
Overpaying "earns" your mortgage rate, guaranteed and tax-free. Compare that against what savings actually pay after tax, and the higher number wins — with two caveats. Keep an emergency fund first: overpaid money is hard to get back without borrowing again (unless you have an offset mortgage, which delivers similar benefits with full access). And clear genuinely expensive debt — cards, unsecured loans — before feeding the cheapest debt you'll ever hold.
Making it systematic
The habit beats the windfall: a standing order for £100–£200 extra a month, set and forgotten, typically shaves years off a term. At remortgage time, tell your broker you're an overpayer — allowance generosity differs between otherwise similar deals, and it should inform which you pick. Get matched with a remortgage broker through Nesto — free, no obligation.
Frequently asked questions
How much can I overpay without penalty?
Typically 10% of the balance per year on fixed deals; some lenders allow 20%, and tracker/SVR products are often unlimited. Check your specific terms.
Is it better to overpay monthly or as a lump sum?
Mathematically similar for the same total — earlier is better in both cases. Monthly suits budgeting; lump sums suit bonuses. Both must respect the annual allowance.
Should I overpay or invest?
Overpaying is a guaranteed, tax-free return at your mortgage rate; investing offers higher potential with risk. Many people split. Emergency fund and expensive debts come first either way.
Do overpayments reduce my monthly payment?
Only if you ask for that treatment — the default varies. Keeping payments level and shortening the term saves more interest.