Guide
How mortgage overpayments work and why they save more than you expect
A plain guide to what happens when you pay more than your required monthly mortgage payment and why the saving compounds over time.
Every extra pound reduces the principal
Your required monthly payment splits between interest and principal. When you overpay, the extra goes directly to the principal. A smaller principal means less interest is charged the following month, which means more of your regular payment also hits the principal. The effect compounds across the remaining term.
The saving grows with time remaining
An overpayment made early in a long mortgage saves more than the same overpayment made near the end. If you have 20 years remaining, each pound you overpay reduces interest across two decades. If you have 3 years left, the window is much shorter. This is why starting an overpayment strategy as early as possible matters.
Check early repayment charges first
Many fixed-rate mortgages allow overpayments of up to 10% of the outstanding balance per year without a fee. Exceeding that threshold can trigger an early repayment charge that partly or fully cancels the saving. Confirm the rules with your lender or check your mortgage offer before making extra payments.