What Is an Interest-Only Mortgage?
An interest-only mortgage is a type of home loan where your monthly payments cover only the interest charged by the lender. Unlike a repayment mortgage, you do not pay down any of the capital (the amount you borrowed) during the mortgage term. At the end of the term, you must repay the entire original loan amount in full.
This arrangement results in significantly lower monthly payments, making it an attractive option for some borrowers. However, it comes with the critical requirement of having a reliable plan — known as a repayment vehicle — to clear the debt when the mortgage ends.
Interest-Only vs Repayment Mortgage: A Comparison
The table below illustrates the difference between interest-only and repayment mortgages on a £250,000 loan at 4.5% over 25 years:
| Interest-Only | Repayment | |
|---|---|---|
| Monthly payment | £938 | £1,390 |
| Total interest paid | £281,250 | £167,000 |
| Capital repaid during term | £0 | £250,000 |
| Amount owed at end of term | £250,000 | £0 |
| Total cost | £531,250 | £417,000 |
Whilst the monthly saving is substantial (£452 per month in this example), the total cost of an interest-only mortgage is considerably higher because you pay interest on the full balance for the entire term.
Repayment Vehicle Requirements
Since the 2008 financial crisis, UK lenders have become much stricter about interest-only mortgages. To be approved, you typically need to demonstrate a credible repayment vehicle. Commonly accepted options include:
- ISAs and investment portfolios — Regular contributions to stocks and shares ISAs or other investments that are projected to grow sufficiently.
- Sale of another property — If you own additional property, proceeds from its sale can be used.
- Pension lump sum — The tax-free lump sum from a pension (up to 25% of the pot) may be acceptable.
- Endowment policies — Less common now, but still accepted where policies are in place.
- Savings — Existing cash savings or a structured savings plan.
Your lender will normally review your repayment vehicle periodically during the mortgage term to ensure it remains on track.
Who Qualifies for an Interest-Only Mortgage?
Eligibility for residential interest-only mortgages is now more restrictive. Most lenders require:
- Minimum income — Often £75,000 or more per year (some lenders set the threshold at £100,000).
- Low LTV — Typically 75% or below, meaning you need at least a 25% deposit or equivalent equity. Check your loan-to-value ratio to see where you stand.
- Proven repayment vehicle — As detailed above.
- Strong credit history — Lenders want assurance you are a low-risk borrower.
For buy-to-let mortgages, interest-only remains the norm and is much more widely available. See our buy-to-let mortgage calculator for more information.
Pros and Cons of Interest-Only Mortgages
Advantages
- Lower monthly payments — Frees up cash flow for other investments or expenses.
- Flexibility — You may be able to invest the difference and potentially earn higher returns.
- Useful for short-term ownership — If you plan to sell the property within a few years, lower payments can make sense.
Disadvantages
- No capital repaid — You still owe the full loan amount at the end of the term.
- Higher total cost — You pay more interest overall compared to a repayment mortgage.
- Repayment risk — If your repayment vehicle underperforms, you may not be able to clear the debt.
- Stricter eligibility — Fewer products available and higher entry requirements.
- Equity builds slowly — Your mortgage deposit effectively stays the same throughout the term unless property values rise.
Part-and-Part Mortgages
If a fully interest-only mortgage does not suit your needs, consider a part-and-part mortgage. This splits your loan so that a portion is on a repayment basis and the remainder is interest-only. It offers a middle ground: lower payments than a full repayment mortgage, but with some capital being paid off during the term.