Mortgage Overpayments UK: How Much Can You Save?

How Mortgage Overpayments Work

When you overpay your mortgage, the extra money goes directly towards reducing your outstanding capital balance — not future interest. Because interest is calculated on the remaining balance, every pound you overpay reduces the interest you'll be charged going forward.

There are two ways to overpay:

• Regular overpayments — increase your monthly payment by a set amount (e.g. £100 extra per month)
• Lump sum overpayments — make one-off payments when you have spare cash (bonus, inheritance, savings)

When you overpay, you can usually choose to either reduce your monthly payment (keeping the same term) or reduce your term (keeping the same payment). Reducing the term typically saves you more money overall.

How Much Could You Save?

The savings from overpaying can be substantial. Here's an example:

• Mortgage: £200,000 over 25 years at 4.5%
• Normal monthly payment: ~£1,111
• Overpaying £100/month: saves ~£21,000 in interest and pays off the mortgage ~3.5 years early
• Overpaying £200/month: saves ~£36,000 in interest and pays off ~6 years early
• One-off £10,000 lump sum in year 1: saves ~£12,000 in interest over the term

The earlier in your mortgage term you overpay, the greater the benefit — because there's more time for the reduced balance to compound savings.

Overpayment Limits and Early Repayment Charges

Most fixed-rate mortgages allow you to overpay up to 10% of the outstanding balance per year without penalty. Go over this limit and you'll face an Early Repayment Charge (ERC), typically 1–5% of the amount exceeding the allowance.

Key points to check:

• What's the annual overpayment allowance? — usually 10%, but some lenders offer more
• Is the allowance cumulative? — most lenders reset it each year; unused allowance doesn't roll over
• When does the ERC period end? — ERCs usually apply during the fixed or discounted period only
• Tracker and SVR mortgages — often have no ERC at all, meaning unlimited overpayments

Always check your mortgage terms or ask your lender before making large overpayments. See our guide on mortgage fees for more on ERCs.

Should You Overpay or Save?

The general rule: if your mortgage interest rate is higher than the savings rate you can earn (after tax), overpaying is better.

For example, if your mortgage rate is 4.5% and the best savings account pays 3% (before tax), overpaying gives you a guaranteed, tax-free return of 4.5%.

However, you should keep an emergency fund (typically 3–6 months' expenses) before aggressively overpaying — because once the money goes into your mortgage, you usually can't get it back easily.

Some exceptions where saving might be better:

• You're saving for a specific goal (e.g. a deposit on another property)
• You have high-interest debts to clear first (credit cards, loans)
• Your employer matches pension contributions (free money)
• You have an offset mortgage that lets savings reduce interest without locking money away

Offset Mortgages: The Best of Both Worlds?

An offset mortgage links your savings account to your mortgage. Instead of earning interest on your savings, the savings balance is offset against your mortgage balance, reducing the interest charged.

For example, with a £200,000 mortgage and £30,000 in savings, you'd only be charged interest on £170,000. Your savings remain accessible — you can withdraw them at any time.

Offset mortgages are ideal if you want the benefits of overpaying while keeping access to your cash. The trade-off is that offset rates are usually slightly higher than standard fixed rates.

Smart Overpayment Strategies

Here are practical ways to overpay effectively:

1. Round up your payments — if your payment is £987, round it up to £1,000. You'll barely notice the difference.
2. Use pay rises — when your salary increases, put the extra straight into your mortgage before you adjust your lifestyle.
3. Annual bonus — put all or part of annual bonuses towards a lump sum overpayment.
4. Review at remortgage — when you remortgage, consider keeping your payments the same even if your new rate is lower.
5. Use your 10% allowance — calculate your annual allowance and set up a standing order to max it out monthly.

When Not to Overpay

Overpaying isn't always the best use of your money:

• No emergency fund — build up 3–6 months' expenses first
• High-interest debt — clear credit cards and loans before your mortgage
• No pension contributions — employer-matched pension is effectively free money and should come first
• ERC would exceed savings — if you'd breach your overpayment limit, the charge may outweigh the benefit
• Very low mortgage rate — if your rate is below inflation, there may be better uses for your cash