Mortgage Repayment & Overpayment Comparison Calculator
Calculate the exact interest savings and term reduction from overpaying your mortgage. Even small regular overpayments save thousands over the mortgage term.
Mortgage Overpayment Guide
Why Overpaying Your Mortgage Is Powerful
Every extra pound paid reduces the outstanding balance, which reduces the interest charged in subsequent months. This compound effect means overpayments made early in a mortgage save significantly more than overpayments made later. Example: a £200,000 mortgage at 4.5% over 20 years has standard monthly payments of approximately £1,265. Overpaying by £200/month saves approximately £22,000 in interest and reduces the term by over 3 years. The earlier in the mortgage term you overpay, the greater t
The 10% Annual Overpayment Limit
Most fixed-rate UK mortgages allow overpayments of up to 10% of the outstanding balance per year without an Early Repayment Charge (ERC). Check your mortgage terms before overpaying — ERCs on fixed-rate mortgages can be 1-5% of the amount overpaid, making excessive overpayment costly. On tracker or standard variable rate mortgages, there is typically no ERC, so unlimited overpayment is permitted. Some lenders (Nationwide, Halifax, NatWest) apply the 10% to the original loan amount rather than th
Overpay vs Invest
The decision whether to overpay your mortgage or invest surplus cash depends on: mortgage rate vs expected investment return. If mortgage rate > expected return: overpay (guaranteed saving vs uncertain gain). If expected return > mortgage rate: consider investing (but remember investment returns are not guaranteed). In 2026/27 context: mortgages at 4.5-6.5% vs long-term stock market average of ~7% — the decision is close and personal risk tolerance matters. Tax-free ISA returns make the investme
Offset Mortgages
An offset mortgage links your savings account balance to your mortgage — reducing the mortgage balance on which interest is calculated. Example: £200,000 mortgage with £30,000 in the linked savings account = interest charged on £170,000 only. You keep access to the savings while they effectively earn a return equal to the mortgage rate (currently 4-6%). Particularly tax-efficient for higher-rate taxpayers because there is no interest income to declare — the benefit is received as reduced interes
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