Loan Overpayments and Amortisation

Last reviewed: 8 October 2026

Amortisation is the process of paying a loan down through scheduled payments. Each payment normally includes interest and principal. Overpayments can accelerate that process by reducing the balance sooner.

How the schedule changes

For a fixed-rate loan, the monthly payment may stay the same while its composition changes. Early payments usually contain more interest because the outstanding balance is higher.

Why overpayments can save interest

If an extra payment is applied to principal, future interest is calculated on a lower balance. Regular overpayments can therefore reduce total interest and shorten the repayment period.

Monthly overpayment versus lump sum

A monthly overpayment adds the same extra amount each month. A lump sum reduces the balance at one point in time. The earlier the balance is reduced, the longer it can affect future interest.

Check the agreement

Some loans or mortgages have early-repayment charges, annual limits or rules about how extra payments are applied. A calculator cannot know those contract details.

Keep enough cash available

Paying debt down faster can reduce interest, but it also uses cash that might otherwise be available for emergencies. The calculator shows arithmetic, not whether overpaying is suitable for you.

Official consumer guidance

MoneyHelper discusses early repayment and possible charges in its personal loans guide.

Loan Amortisation Calculator →
Early Loan Repayment Calculator →