Almost every UK residential mortgage is a repayment mortgage: each monthly payment covers a slice of capital and a slice of interest, so the loan is fully cleared at the end. Interest-only is the exception — common for buy-to-let, rare and tightly restricted for owner- occupied homes. Below: the mechanics, the cost difference, and when each one makes sense.

How each one actually works

Repayment. The standard structure for UK home mortgages. Each monthly payment is calculated by the amortisation formula:

M = P × r × (1+r)ⁿ / ((1+r)ⁿ − 1)

where P is the loan, r is the monthly interest rate (annual rate divided by 12), and n is the term in months. The payment stays constant across the full term (for a given rate), but the split between capital and interest shifts — early payments are mostly interest, later payments mostly capital. By the end, the loan is fully repaid.

Interest-only. The monthly payment is simply the loan multiplied by the annual rate, divided by 12. The capital balance never reduces — it's still owed in full at term end, when you'll need to repay it from savings, the sale of an investment, or another agreed source.

The cost difference in numbers — £250,000 over 25 years at 4.5%

Metric	Repayment	Interest-only
Monthly payment	£1,390	£938
Total monthly payments over 25 years	£416,900	£281,300
Capital owed at term end	£0	£250,000
Total cost over term	£416,900	£531,300
Total interest paid	£166,900	£281,300

Interest-only costs around £114,000 more over 25 years on this loan, because every month interest is charged on the full £250,000 balance rather than a falling balance. The trade-off: monthly cash flow is £452 lower on interest-only.

Run the same comparison at your loan, rate and term on the mortgage repayment calculator.

When interest-only is the right choice

• Buy-to-let. The dominant choice for landlords. Rent covers the interest, the capital sits unpaid until sale or refinance, and landlords prioritise yield over equity growth.
• High-net-worth applicants. Borrowers with significant liquid assets sometimes prefer interest-only to keep cash flow flexible — repaying capital from investments or business proceeds at term end.
• Downsizing borrowers approaching retirement. A borrower planning to sell and downsize in 10–15 years may use interest-only to keep payments manageable, with the property sale as the repayment vehicle.
• Bridging finance. Short-term interest-only is standard for bridging loans between sale and purchase.

When interest-only is the wrong choice

• First-time buyers without a clear repayment vehicle. The cash-flow saving feels attractive but you're not building equity; if property prices fall, you're more exposed to negative equity than a repayment borrower would be.
• Borrowers without disciplined savings. If the saved monthly difference isn't actually invested toward the capital repayment, you'll arrive at term end with a large debt and no way to clear it.
• Anyone who can comfortably afford repayment. The extra £450/month on a £250k mortgage feels meaningful in the short term, but the £114k of extra total cost dwarfs it.

The "interest-only maturity cliff"

The FCA has flagged repeated concerns about UK borrowers reaching the end of an interest-only mortgage without a clear plan to repay the capital. As of 2024 there were still around 750,000 outstanding interest-only mortgages in the UK, many taken out in the 2000s. The maturity cliff refers to the bunched expiry dates in the late 2020s and 2030s — borrowers approaching term end with no repayment vehicle in place.

Lenders increasingly require evidence of a repayment vehicle at application and at remortgage. If you're considering interest-only, plan how the capital will be repaid before you sign, not after.

Part-and-part — the middle option

Some lenders offer a hybrid: a portion of the loan on repayment and the remainder on interest-only. Useful when:

• You want to keep monthly cash flow lower than full repayment but maintain some equity build.
• You have a partial repayment vehicle covering some but not all of the capital.
• You're approaching retirement and want some of the loan cleared before then.

Typical splits are 50/50, 75/25 (repayment-heavy) or 25/75 (interest-only- heavy). Lender choice is narrower than for either pure structure.

Switching during the mortgage

Most UK mortgages allow you to switch between structures during the term:

• Interest-only to repayment. Common. Your monthly payment rises because you're now paying down capital. The lender will re-test affordability before approving the switch.
• Repayment to interest-only. Tightly restricted on residential mortgages — typically only allowed in specific hardship cases or for borrowers meeting the lender's high-net-worth criteria.
• Switching at remortgage. The easiest time to change structures — a new product with a new lender effectively resets the clock.

How rate affects each one differently

Both structures get more expensive when rates rise, but interest-only is more sensitive in percentage terms because every pound of the original balance is exposed for the full term.

Worked example on the same £250,000 / 25-year loan:

Rate	Repayment monthly	Interest-only monthly
3.5%	£1,252	£729
4.5%	£1,390	£938
5.5%	£1,535	£1,146
6.5%	£1,688	£1,354

Test the impact on your numbers using the mortgage stress test calculator.

What lenders ask for if you want interest-only

• Repayment strategy evidence. Investment statements, expected inheritance documentation, business sale plans, or a credible downsizing plan.
• Higher minimum income. Often £75,000+ individual or £100,000+ joint for interest-only residential products.
• Lower maximum LTV. Typically capped at 50–75% LTV vs 90–95% for repayment.
• Annual reviews. Some lenders require periodic check-ins on the repayment vehicle during the term.

Frequently asked questions

What's the difference between repayment and interest-only?

On a repayment mortgage, each monthly payment includes capital and interest, so the loan is fully cleared at the end of the term. On interest-only, you pay only the monthly interest — the full capital balance is still owed at the end. Monthly payments are lower on interest-only, but the total cost (including the capital repayment) is roughly the same as repayment over the life of the loan.

Is interest-only cheaper than repayment?

The monthly payment is lower because you're not paying down the capital. The total cost is similar or higher once you include the capital repayment at the end. Interest-only is about cash-flow timing, not total saving.

Can first-time buyers get interest-only mortgages?

Rarely. Most UK lenders restrict interest-only residential mortgages to high-net-worth applicants, older borrowers downsizing, or those with a credible repayment vehicle (significant savings, investment portfolio, sale of another property). First-time buyers without those backstops will almost always be offered repayment only.

What happens at the end of an interest-only mortgage?

The full capital balance becomes due — typically the original loan amount. You'll need to repay it from savings, the sale of an investment, the sale of another property, or by remortgaging onto a new product. A growing concern for the UK regulator is the "interest-only maturity cliff" — borrowers reaching term-end without a clear repayment plan.

Is interest-only used for buy-to-let?

Yes — it's the default for buy-to-let. Landlords typically use interest-only mortgages to keep monthly costs low (rent must cover the interest plus a stress-test margin), and either repay the capital from the property sale or refinance indefinitely.

Can I switch from interest-only to repayment?

Yes — most lenders allow you to switch during the mortgage term, often called "converting". Your monthly payment will increase because you're now repaying capital each month. You can also part-and-part: keep some of the balance on interest-only and switch the rest to repayment.

Which option costs less in total?

On the maths of a constant rate held across the term, repayment costs slightly less in total because the balance falls month by month, so the interest charged is lower. Interest-only charges interest on the full original balance every month. Over 25 years on a £250,000 mortgage at 4.5%, repayment totals around £417,000 of payments; interest-only totals around £281,000 of payments plus the £250,000 capital owed at term end — roughly £531,000 all-in.

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Last reviewed: 24 May 2026.