Interest-Only vs Repayment Mortgages: Which Is Right for You?

A capital and interest mortgage (also called a repayment mortgage) requires monthly payments that cover both the interest on the outstanding loan and a portion of the capital. Each payment reduces the debt outstanding. By the final payment, the mortgage is fully repaid and the borrower owns the property outright. This is the most common structure for residential owner-occupier mortgages in the UK.

An interest-only mortgage requires monthly payments that cover only the interest on the outstanding loan. The capital does not reduce. After 25 years on an interest-only mortgage, the full original loan amount is still outstanding and must be repaid in a single payment. This requires a separate capital repayment vehicle - an investment, a planned property sale, a pension lump sum, or another specific strategy.

Use our interest-only vs repayment calculator to model the exact monthly payment difference, total interest cost, and projected equity position for your specific loan amount, rate, and term.

The monthly payment difference between the two structures is significant. On a £300,000 mortgage at 4.75% over 25 years: capital and interest costs approximately £1,694 per month; interest-only costs approximately £1,188 per month - a difference of £506 per month (£6,072 per year). Over 25 years, the total interest paid on the capital and interest mortgage is approximately £208,000. The total interest paid on the interest-only mortgage is approximately £356,000 - £148,000 more - because the capital balance never reduces and interest accrues on the full £300,000 throughout.

The interest-only borrower also faces a £300,000 capital repayment at the end of the term. If the repayment vehicle (property sale, investment, pension) performs as expected, this is manageable. If it does not, the borrower faces a serious problem at the end of a very long mortgage term.

Investors and portfolio builders: For borrowers whose primary goal is capital growth rather than debt elimination, interest-only makes strategic sense. A property investor who plans to sell the property at the end of the term (using the proceeds to repay the mortgage and retain the capital growth) is using the mortgage cost-effectively. The lower monthly payment improves cashflow, which can be redeployed into further investments.

Short-term borrowing: For a planned short-term mortgage - a borrower who intends to sell the property within five to ten years - interest-only minimises monthly cost while the property appreciates. The lower payment preserves capital for other purposes.

Borrowers with variable income: Self-employed borrowers or commission-earners with significant income variability may prefer the lower obligatory payment of interest-only, with flexibility to overpay when income is high. However, lenders require a credible repayment vehicle even in these cases - the approach must be planned.

Later-life borrowers: Retirement interest-only mortgages are a specific product designed for borrowers aged 55+ who want to keep monthly payments low (using retirement income to service the interest) while retaining the property. The loan is repaid on death or entry into care.

Capital and interest is the right choice for the majority of residential owner-occupiers because it: guarantees the property is owned outright at the end of the term; eliminates the risk of the repayment vehicle underperforming; builds equity with every payment rather than leaving the full debt outstanding; and is accepted by all mortgage lenders without the additional requirement to evidence a repayment strategy.

For first-time buyers, home movers, and any borrower whose primary goal is owning their home outright, capital and interest is both the right product and the most widely available one. The higher monthly payment is the price of certainty and debt elimination.

Since the Mortgage Market Review (MMR) of 2014, lenders have been required to assess the suitability of interest-only residential mortgages, including whether the borrower has a credible capital repayment vehicle.

The strength of the repayment vehicle evidence affects which lenders will accept an interest-only residential mortgage and at what LTV - typically a maximum of 75% LTV.

A part-and-part mortgage splits the loan between capital and interest (reducing the debt on part of the loan with each payment) and interest-only (maintaining the balance on the remainder). This allows borrowers to keep monthly payments lower than a full repayment mortgage while still reducing some of the debt over time.

Some lenders offer this structure; others prefer the borrower to choose one approach for the full loan. For borrowers who want the certainty of some debt reduction but need the cashflow benefit of lower payments, part-and-part is worth exploring.