The cheaper monthly option is usually interest-only, but that does not mean it is the cheaper or safer mortgage overall. A repayment mortgage costs more each month because you repay interest and capital together; an interest-only mortgage keeps the monthly payment lower but leaves the original loan balance to be repaid later.
For most residential buyers, the main question is not just “which monthly payment is lower?” It is “what happens to the mortgage balance by the end of the term?”
Compare both payment types with your numbers
Use our UK Mortgage Repayment Calculator to compare repayment and interest-only monthly payments side by side.
Quick comparison: repayment vs interest-only
A repayment mortgage gradually clears the debt. An interest-only mortgage only covers the interest, so the full loan balance remains outstanding unless you repay it another way.
| Feature | Repayment mortgage | Interest-only mortgage |
|---|---|---|
| Monthly payment | Higher, because you pay interest and capital | Lower, because you only pay interest |
| Mortgage balance | Designed to reduce to zero by the end of the term | Usually remains the same unless you make separate capital repayments |
| Main risk | Higher monthly commitment | Needing to repay the full capital balance at the end |
| Typical residential use | Common for owner-occupiers | Usually harder to get and needs a credible repayment plan |
| Best suited to | Borrowers who want the debt cleared automatically over time | Borrowers with a strong repayment strategy accepted by the lender |
Example: £250,000 mortgage at 5% over 25 years
The monthly payment difference can look attractive at first. On a £250,000 mortgage at 5% over 25 years, the interest-only payment is much lower than the repayment option.
| Mortgage type | Estimated monthly payment | Total interest over 25 years | Balance left at end |
|---|---|---|---|
| Repayment | £1,461.48 | £188,442.53 | £0 |
| Interest-only | £1,041.67 | £312,500.00 | £250,000 |
| Difference | Interest-only is £419.81 cheaper each month | Interest-only pays £124,057.47 more interest over the term | Interest-only still needs the original loan repaid |
This is the key trade-off. Interest-only can make the monthly payment easier, but the mortgage balance does not disappear. You still need a reliable plan for the £250,000 capital.
Important: a lower monthly payment can hide a bigger long-term problem if there is no realistic way to repay the capital at the end.
How a repayment mortgage works
A repayment mortgage is designed to clear the debt by the end of the mortgage term. Each monthly payment includes interest and a portion of the original loan.
In the early years, more of the payment usually goes towards interest because the balance is still high. As the balance falls, more of each payment goes towards capital.
This is why repayment mortgages are often easier to understand. If you keep up with the agreed payments and the mortgage runs to the end of the term, the loan should be fully repaid.
- Main benefit: the mortgage balance should reduce over time.
- Main drawback: the monthly payment is higher than interest-only.
- Best for: borrowers who want a clear route to owning the home outright.
How an interest-only mortgage works
An interest-only mortgage works differently. The monthly payment covers the interest due, but it does not repay the original capital unless you make separate payments.
That means a £250,000 interest-only mortgage can still leave £250,000 outstanding at the end of the term. The lender will usually want to see a credible repayment plan before agreeing to this structure.
Possible repayment plans can include savings, investments, pension-related plans, sale of another property, sale of the mortgaged property, or other assets. The key point is that the plan must be realistic and acceptable to the lender.
- Main benefit: lower monthly payments.
- Main drawback: the original balance still needs to be repaid.
- Best for: borrowers with a strong capital repayment strategy and lender approval.
Why interest-only can be riskier
The risk is not the interest payment itself. The risk is reaching the end of the mortgage term without the money to repay the capital.
If the repayment plan underperforms, the borrower may need to sell the property, extend the mortgage, switch to repayment, use savings, downsize, or agree another solution with the lender. None of those outcomes should be assumed.
Reality check: if the only plan is “house prices will rise” or “I will sort it out later”, the risk is being pushed into the future rather than solved.
When interest-only might make sense
Interest-only is not automatically bad. It can make sense in specific situations where the borrower understands the risk and has a credible repayment route.
- Buy-to-let: many landlords use interest-only because rental yield and tax planning are different from residential borrowing.
- Later-life borrowing: some older borrowers may use retirement interest-only products where suitable.
- Irregular income: some borrowers may prefer lower required monthly payments and make lump-sum repayments when income arrives.
- Asset-backed repayment: some borrowers may have investments, savings or another property intended to clear the balance.
Even then, the lender must be satisfied. Factors such as loan-to-value and credit profile matter too — a borrower wanting lower monthly payments is not enough on its own.
When repayment is usually better
Repayment is usually better when the priority is certainty. It gives a clear path where the balance reduces as long as the borrower keeps up with payments.
It is often the more suitable structure for first-time buyers, home movers and borrowers who do not have a separate capital repayment plan.
- You want the mortgage cleared by the end of the term.
- You do not have a separate investment or asset plan to repay the capital.
- You want less risk at retirement or later life.
- You prefer the discipline of automatic capital repayment.
- You want to reduce your balance and improve equity over time.
Check affordability before choosing repayment
Use our Mortgage Affordability Calculator to test whether the higher repayment mortgage payment fits your income and commitments.
Can you switch between repayment and interest-only?
It may be possible to switch, but it is not automatic. Moving from interest-only to repayment usually increases the monthly payment because you start repaying capital as well as interest.
Moving from repayment to interest-only may reduce the payment, but lenders normally apply strict checks. They may want to understand why the change is needed and how the capital will be repaid.
If affordability is the reason for switching, speak to the lender early. Options can depend on your mortgage product — whether fixed-rate or variable — payment history, income, term remaining and the lender’s criteria.
Decision guide: which one should you choose?
The right structure depends on your cash flow, risk tolerance and repayment plan. The table below gives a simple way to think about it.
| Your situation | Usually points towards | Why |
|---|---|---|
| You want the mortgage cleared automatically | Repayment | The balance is designed to reduce each month |
| You need the lowest monthly payment | Interest-only may look cheaper | But the capital still needs a repayment plan |
| You have no separate repayment strategy | Repayment | Interest-only creates a large future repayment problem |
| You have a credible asset-backed repayment plan | Interest-only may be considered | The lender still needs to accept the plan |
| You are a typical first-time buyer | Repayment | It gives a clearer path to reducing the debt |
Common mistakes to avoid
The biggest mistake is judging the mortgage only by the monthly payment. That makes interest-only look attractive while ignoring the capital balance.
- Ignoring the final balance: interest-only does not make the original loan disappear.
- Assuming investments will perform: investment values can rise or fall, so the repayment plan needs monitoring.
- Forgetting the term end date: the repayment problem becomes urgent if left too late.
- Comparing monthly payments only: total interest and remaining balance matter too.
- Choosing interest-only because repayment feels expensive: that may be a sign the mortgage amount itself is too high.
Repayment vs interest-only mortgage FAQs
Is repayment or interest-only cheaper?
Interest-only is usually cheaper each month because you only pay interest. Repayment is usually safer for most homeowners because the balance is designed to reduce over time.
What happens at the end of an interest-only mortgage?
The original mortgage balance still has to be repaid. You need a credible repayment plan, such as savings, investments, property sale or another lender-accepted strategy.
Can I switch from interest-only to repayment?
It may be possible, but your monthly payment will usually increase. That is because you start repaying capital as well as interest, so the lender needs to check affordability.
Why are interest-only mortgages harder to get?
Lenders usually need confidence that you can repay the capital at the end of the term. That makes the checks stricter than simply asking whether you can afford the monthly interest.
Is interest-only a good idea for first-time buyers?
Usually not for most first-time buyers unless there is a strong repayment plan and a lender is willing to accept it. A repayment mortgage is normally clearer because the debt reduces over time.
Ready to compare mortgage options?
Once you understand the monthly cost and the capital repayment risk, compare mortgage deals or speak to a broker before choosing a mortgage type.
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Sources used for factual context: MoneyHelper guidance on repayment and interest-only mortgages, MoneyHelper guidance on repaying interest-only mortgages, and FCA interest-only mortgage borrower guidance/work. Check lender criteria before publication updates.