The 10% mortgage overpayment rule explained
Most UK fixed-rate and tracker mortgages let you overpay up to 10% of the outstanding balance each year without an early-repayment charge. This is the rule you will see quoted on lender websites, comparison tables, and annual mortgage statements. The catch is that every lender interprets the details differently, so "10%" is more of a starting point than a universal limit.
What does the 10% rule mean?
The 10% rule usually means you can pay off up to 10% of the mortgage balance in a calendar year or deal-year without penalty. The exact base depends on the lender. Some use the original loan amount at the start of the deal. Others use the outstanding balance at the start of each calendar year or the anniversary of the mortgage start date. A few use the balance on the date of the overpayment.
Because of that variation, two borrowers with the same balance and the same 10% headline could face very different limits. A lender using the original loan amount might let you overpay far more than a lender using the current balance, especially in the early years. A lender using the current balance gives a smaller allowance as the debt shrinks.
Why do lenders set the limit?
Lenders borrow money to fund your mortgage, often at fixed rates from the wholesale market. If you repay early during a fixed-rate period, they may still be paying for funds they no longer need. The early-repayment charge, or ERC, is how they recover some of that cost. The 10% allowance is a compromise: it gives borrowers flexibility while protecting the lender from large unscheduled repayments.
The Financial Conduct Authority expects lenders to treat customers fairly and to set out charges clearly in the mortgage offer and terms. Your mortgage illustration and offer letter should spell out the overpayment allowance and the ERC percentage. If they do not, ask your lender or broker before you overpay.
What happens if you overpay more than 10%?
If you pay above the allowance, the lender can charge an ERC on the excess amount. A typical ERC during a fixed-rate period might be 3% to 5% of the overpaid amount. On a £10,000 overpayment above the allowance, that could be £300 to £500. That charge can wipe out most or all of the interest saving from the overpayment.
Some lenders do not charge ERCs at all. Others charge a flat fee or a percentage that tapers down over the deal period. A few allow unlimited overpayments once you are on the standard variable rate. The only way to know for sure is to read your mortgage terms or ask your lender.
How to check your personal allowance
Start with your mortgage offer. Look for the section on early repayment, overpayments, or ERCs. It should state the percentage, the basis on which it is calculated, and any fees. Then check your latest annual mortgage statement, which often shows how much of the allowance you have used in the current year.
If you are unsure, call your lender and ask two questions: how much can I overpay this year without a charge, and how is the 10% calculated? Write down the date and the answer. This matters because a mistake can be expensive to undo.
Does the 10% rule apply on the standard variable rate?
Usually not. Once a fixed or tracker deal ends and you move to the lender's standard variable rate, the overpayment rules are typically much more generous. Many lenders allow unlimited overpayments on their SVR. This is one reason some borrowers choose to overpay aggressively once they revert to the SVR, even though the SVR itself is usually higher than a fixed rate.
The trade-off is that the interest rate on the SVR is often higher, so the mortgage is costing more month to month. If you are disciplined enough to overpay, the unlimited allowance can still make the SVR a useful window for clearing debt. If you are not overpaying, remortgaging to a new deal is usually better than staying on the SVR.
Is the 10% rule enough to clear a mortgage early?
For most households, 10% of the outstanding balance per year is a generous allowance. On a £250,000 mortgage, that is up to £25,000 a year. Most borrowers do not have that much spare cash, so the practical limit is their monthly budget, not the lender's cap. If you can only afford £200 or £500 a month, you are unlikely to hit the 10% limit.
If you receive a large lump sum, such as an inheritance or bonus, the 10% cap becomes more relevant. In that case, timing matters. You might want to pay the lump sum early in the year so you can make another overpayment the following year, or split it across two tax years to stay within two allowances. Some borrowers choose to remortgage to a deal with a higher allowance or no ERCs.
What about reducing the term versus reducing the payment?
When you overpay, your lender may ask whether you want to shorten the term or reduce the monthly payment. Shortening the term keeps the payment the same and clears the mortgage faster, which saves the most interest. Reducing the payment keeps the term the same but lowers your monthly cost, which can help cash flow.
Most UK lenders default to shortening the term for small overpayments. If you want the opposite, you usually need to request it. Think about your goal before you overpay. If you want to be mortgage-free sooner, ask for the term to be reduced. If you want lower monthly costs, ask for the payment to be reduced.
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Last updated: 4 August 2026. This article is educational and is not financial advice.