Last reviewed: June 2026
TL;DR- Each monthly payment covers interest plus a portion of the outstanding capital, so the balance reduces every month.
- In the early years the majority of each payment is interest - capital reduction accelerates in the later years of the term.
- Total interest paid is directly affected by the interest rate, loan amount and term length.
- Overpayments reduce the outstanding balance and cut total interest paid - most lenders allow up to 10% of the balance per year without penalty.
How a Repayment Mortgage Works
A repayment mortgage - sometimes called a capital and interest mortgage - requires the borrower to pay both interest and a portion of the outstanding loan with every monthly payment. By the end of the agreed term, the loan is fully repaid and the borrower owns the property outright, assuming all payments have been made on time.
This is the most common mortgage structure in the UK residential market and is the structure the FCA requires lenders to use as the affordability benchmark when assessing all mortgage applications, including those for interest only products.
How Payments Are Calculated
Monthly payments on a repayment mortgage are calculated using an amortisation formula that produces a fixed payment amount - assuming a fixed interest rate - spread over the term. In the early months, the outstanding balance is at its highest, so a larger proportion of each payment is allocated to interest. As the balance reduces, a greater share of each payment goes toward capital.
This structure means that switching to a shorter term increases monthly payments but reduces total interest paid substantially. Extending the term reduces monthly payments but increases total interest paid over the life of the loan.
Affordability Assessment
Under FCA rules set out in MCOB 11, lenders must assess whether borrowers can afford the mortgage on a repayment basis. The assessment uses the lender's stressed interest rate - typically 1-3 percentage points above the product rate - to test affordability if rates rise. Income is assessed net of tax, existing debt commitments, and essential expenditure.
The Bank of England's Financial Policy Committee sets a loan-to-income (LTI) flow limit: no more than 15% of new mortgage lending can be at LTI ratios above 4.5. Most lenders apply a maximum of 4.5 times individual income or 4 times joint income, though some specialist lenders go higher for specific professional groups.
Fixed vs Variable Rate on a Repayment Mortgage
The repayment structure applies regardless of whether the interest rate is fixed or variable. A fixed rate mortgage sets the interest rate for an initial period - typically 2, 3 or 5 years - after which the rate reverts to the lender's standard variable rate (SVR) unless the borrower remortgages. A tracker or variable rate mortgage means monthly payments fluctuate with the base rate or lender SVR throughout the term.
The choice between fixed and variable rate affects the monthly payment amount and total interest cost but does not change the fundamental repayment structure.
Overpayments and Their Effect
Most lenders allow overpayments of up to 10% of the outstanding balance per year without triggering an early repayment charge (ERC). Overpayments reduce the outstanding capital directly, which reduces the interest charged in subsequent months and shortens the effective term of the mortgage.
Underpayments - reducing the monthly payment below the contractual amount - are not permitted under standard repayment mortgage terms without lender agreement. Some flexible mortgages allow underpayments where the borrower has previously overpaid sufficiently.
Term Length Considerations
The standard mortgage term has extended in recent years as affordability pressures have pushed borrowers toward longer terms to reduce monthly payments. The FCA and Bank of England have noted the growth in 35 and 40-year mortgage terms, which lower monthly payments but increase total interest paid and may extend repayment into retirement age.
Lenders assess the term against the borrower's expected retirement age and apply their own maximum age at end of term criteria - commonly 70 to 75 years. Some specialist and later-life lenders extend this further.
Frequently Asked Questions
Is a repayment mortgage always better than interest only?
A repayment mortgage guarantees the loan is cleared by the end of the term. Interest only requires a separate repayment strategy that carries investment or market risk. Which structure suits a borrower depends on their circumstances, financial plans and risk tolerance - a regulated mortgage adviser can assess this.
Can I switch from repayment to interest only?
Some lenders allow a temporary switch to interest only - sometimes called a payment concession - for borrowers experiencing financial difficulty. A permanent switch requires a new affordability assessment and evidence of a credible repayment vehicle, subject to lender criteria and FCA conduct rules.
What happens at the end of a repayment mortgage term?
If all payments have been made, the mortgage is fully repaid and the lender releases the charge on the property. The borrower receives confirmation of redemption and owns the property outright. If payments have been missed, the outstanding balance at term end must be settled before the charge is released.
How does term length affect total cost?
A longer term reduces monthly payments but increases the total interest paid over the life of the loan. A 25-year mortgage and a 35-year mortgage on the same loan amount at the same rate will have meaningfully different total interest costs - the additional 10 years of interest can add tens of thousands of pounds to the total repaid.
