Should you overpay your mortgage?
Overpaying is one of the most reliable ways to save money, but only if you understand the 10% rule, whether to cut the term or the payment, and how it stacks up against saving or investing instead.
Why overpaying saves so much
Every pound you overpay comes straight off the balance, so it stops accruing interest for the entire remaining term. Because mortgage interest is front-loaded, overpayments made early are the most powerful, they remove capital that would otherwise have been charged interest for 20+ years. Even a modest monthly overpayment can knock years off the term and save tens of thousands in interest.
Regular overpayments vs lump sums
Regular monthly overpayments are easy to budget and chip away steadily at the balance. Lump sums, a bonus, inheritance or savings, make an immediate dent and are especially effective early in the mortgage. Both work; the calculator lets you combine them. The earlier and larger the overpayment, the bigger the saving.
The 10% rule and early repayment charges
Most fixed and discounted deals let you overpay up to 10% of the outstanding balance each year without penalty. Go beyond that during the fixed period and you may face an early repayment charge (ERC), often 1 to 5% of the excess. Always check your annual allowance before making a large overpayment. Once you're on the standard variable rate, there's usually no ERC and you can overpay freely.
Confirm before a big lump sum
Reduce the term or the payment?
By default, overpaying keeps your monthly payment the same and shortens the term, this saves the most interest. Some lenders instead let you keep the original term and lower the monthly payment, which helps cash flow but saves less. If your goal is to be mortgage-free sooner and minimise interest, choose to reduce the term.
Overpay, save, or invest?
Overpaying earns a guaranteed, tax-free return equal to your mortgage rate. Compare that to what you'd earn elsewhere: if a savings account pays more than your mortgage rate after tax, saving may win; if you have higher-interest debt, clear that first; and pension contributions can beat overpaying for higher-rate taxpayers thanks to tax relief. An offset mortgage is another way to use savings to cut interest while keeping access to the cash.
Common mistakes
- Breaching the 10% allowance. Overpaying above your annual limit during a fix can cost more in ERC than the interest saved.
- Overpaying before clearing pricier debt. Credit cards and loans usually cost far more than a mortgage, clear them first.
- Leaving no emergency fund. Money overpaid is hard to get back. Keep 3 to 6 months of expenses accessible.
- Reducing the payment instead of the term. If your aim is to save interest, keep the payment and cut the term instead.