Buy-to-Let Interest-Only vs Repayment (2026): Why 80% of Landlords Pick Interest-Only
Are buy-to-let mortgages interest-only? Around 80% are — and for structural reasons, not habit. The worked numbers on cashflow, the ICR maths that decides your maximum loan, the exit strategies lenders will accept, and the honest five-year sum where repayment quietly wins.
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Quick answer
Most buy-to-let mortgages are interest-only — around 80% of the market — and it’s the default for three structural reasons: cashflow, flexibility, and how lenders assess the loan. On a typical £150,000 BTL loan at 5.25%, interest-only costs £656.25 a month against £898.87 on 25-year repayment — about 27% lower — which is the difference between a property that pays you monthly and one that breaks even. Lenders test buy-to-let affordability on rental cover of the interest (ICR, typically 125–145%), not your salary, so the interest-only structure and the lending maths are built for each other. The trade: you still owe the full capital at the end of the term, so lenders require a credible exit strategy — refinance, sale, or savings — nominated up front. And the honest counterpoint most guides skip: over a five-year fix, repayment on that same loan costs £14,557 more in cash but builds £16,605 of equity and pays £2,048 less interest — so if your rent comfortably covers it, repayment is quietly the wealthier route, which is why it suits single-property landlords aiming to own outright by retirement. Interest-only suits portfolio builders who reinvest cashflow, higher-rate taxpayers managing Section 24, and anyone who values the option to overpay without the obligation. Rates as of July 2026: UK Finance puts the average across all new BTL loans at 4.71% (Q1 2026), with typical fixed deals running roughly 4.9–5.8%. Much buy-to-let lending is not regulated by the FCA.
Your property may be repossessed if you do not keep up repayments on your mortgage.
In this guide
Why most buy-to-let is interest-only
Ask “are buy-to-let mortgages interest-only?” and the market answers for you: roughly 80% are, against a residential market where interest-only is the exception needing special justification. (If you’re weighing the two for your own home, that’s a different decision with different rules — our residential interest-only vs repayment guide covers it; this page is the landlord version.) Three structures push BTL toward interest-only:
- Cashflow is the business model. A rental property is a small business; the mortgage is its biggest cost. Interest-only takes ~27% off the monthly payment, converting a break-even property into one producing a monthly surplus that covers voids, maintenance, agent fees — or the deposit on the next property. Portfolio landlords in particular prefer accessible cashflow over equity locked in walls.
- The lending maths is built for it. BTL affordability runs on the interest cover ratio — rent versus interest — not repayment instalments and not your salary. The product and the assessment are two halves of the same design.
- Flexibility beats obligation. Most BTL deals allow overpayments of around 10% a year without penalty. An interest-only landlord can choose to repay capital in good months and stop in bad ones; a repayment landlord must pay £898.87 every month regardless of whether the boiler just died or the tenant just left.
The same logic runs through the specialist cousins — holiday-let and Airbnb lending, and expat BTL — where interest-only likewise dominates. The structural price of all this: nothing is being repaid. Borrow £150,000 today and you owe £150,000 at the end of the term, which is why exit strategy is a lender requirement, not a suggestion.
The worked numbers: IO vs repayment
Take the standard case: a £200,000 property, 25% deposit, £150,000 loan at 75% LTV, on an illustrative 5.25% fix (mid-range of 2026’s typical 4.9–5.8%), rent £900 a month:
| Interest-only | Repayment (25 yrs) | |
|---|---|---|
| Monthly payment | £656.25 | £898.87 |
| Monthly cashflow on £900 rent | +£243.75 | +£1.13 |
| Balance after a 5-year fix | £150,000 | £133,395 |
| Equity built in 5 years | £0 | £16,605 |
| Interest paid over 5 years | £39,375 | £37,327 |
| Owed at end of 25-year term | £150,000 | £0 |
Read both columns honestly. Interest-only turns the property cash-positive by £243.75 a month while repayment leaves £1.13 — before agent fees, maintenance and tax, the repayment version of this property is loss-making month to month. But the five-year ledger cuts the other way: repayment’s extra £14,557 of cash over the fix buys £16,605 of equity and — because the balance shrinks as you go — £2,048 less interest. Neither column “wins”; they’re different machines. One manufactures monthly income and options; the other manufactures ownership.
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The ICR maths: what your rent lets you borrow
This is the calculator behind every BTL “how much can I borrow” answer. Lenders require rent to cover the mortgage interest by an interest cover ratio — typically 125% for basic-rate and limited-company borrowers, 145% for higher-rate taxpayers — calculated at a stress rate. On five-year fixes, many lenders stress at or near the pay rate; shorter fixes get stressed harder, often pay rate plus around 2%. That single difference moves your maximum loan dramatically. For £900 rent:
| Assessment basis | Max loan £900 rent supports |
|---|---|
| 125% ICR at 5.25% pay-rate (5-yr fix, basic-rate/ltd-co) | £164,571 |
| 145% ICR at 5.25% pay-rate (5-yr fix, higher-rate) | £141,872 |
| 125% ICR at 7.25% stress (2-yr fix, basic-rate/ltd-co) | £119,172 |
| 145% ICR at 7.25% stress (2-yr fix, higher-rate) | £102,735 |
Same property, same rent — a £61,836 spread in maximum borrowing depending on tax band and product choice. Two practical notes: first, because ICR is tested on the interest, choosing repayment doesn’t usually shrink your maximum loan — it just demolishes the monthly cashflow, which is exactly why the market pairs the ICR test with interest-only. Second, the market currently has enormous headroom in aggregate — UK Finance measured the average ICR across the UK at 221% in Q1 2026 — meaning typical landlords hold far more rental cover than the minimum, a cushion worth copying rather than borrowing to the wire.
The honest case for repayment
When repayment beats interest-only
The 20% of the market on repayment isn’t wrong — it’s running a different strategy. Repayment suits: the single-property landlord whose plan is a mortgage-free rental producing retirement income, letting the tenant clear the debt over 20–25 years; strong-yield properties where rent covers the repayment instalment with margin, so the cashflow sacrifice is affordable; and anyone uneasy nominating an exit strategy — repayment is the exit strategy. There’s also a middle path most landlords underuse: take interest-only, then overpay voluntarily within the usual 10%-a-year allowance. You capture repayment’s equity-building whenever cashflow allows, while keeping the contractual payment at £656.25 for the months when it doesn’t. Discipline required; flexibility retained.
Exit strategies lenders accept
Every interest-only BTL application nominates how the capital gets repaid. Lenders accept three, and mixing is fine:
- Refinance — the path most landlords actually follow: at the end of each fix, remortgage onto the next product and keep rolling. It works while rates, values and your circumstances cooperate — remembering lenders will still want an end-game as you approach later life.
- Sale of the property — sell at term end, repay the balance, keep the equity. Credible if you’d genuinely sell; be honest with yourself, since properties held 25 years tend to become retirement income their owners never sell. Selling also crystallises capital gains tax — factor it into the sum.
- Savings and investments — ISAs, pensions, other assets; lenders ask for evidence, not intentions.
Two strategic variants worth naming: investors running buy-refurbish-refinance use the post-works revaluation as a built-in partial exit, and established landlords sometimes release equity from existing properties to recycle into the next purchase — powerful, but it raises portfolio-wide leverage, so it deserves modelling, not momentum.
The tax dimension: Section 24 and limited companies
Interest-only maximises your interest bill by design — which collides with how landlord interest is taxed. For personal landlords, Section 24 restricts relief on that interest to a flat 20% credit: basic-rate landlords are broadly unaffected, but higher-rate landlords are taxed at 40% on income that funds a mortgage credited back at only 20% — and the bigger the interest, the wider the gap. A limited company escapes the restriction entirely, deducting interest in full against corporation tax, which is why most new higher-rate BTL borrowing now runs through company structures — and why the IO-versus-repayment choice and the personal-versus-company choice should be made together, with a tax adviser on one side and a broker on the other. One more 2026 context note: the Renters’ Rights Act (in force since 1 May 2026) has lengthened possession timelines and tightened obligations, making the cashflow cushion interest-only provides more valuable, not less — but also making casual landlording harder. Structure accordingly.
The bottom line
Interest-only dominates buy-to-let because the whole machine — ICR assessment, cashflow economics, portfolio building, overpayment flexibility — is engineered around it: £656.25 a month against £898.87 on our worked £150,000 loan, and a property that pays £243.75 a month instead of £1.13. But it’s a structure, not a free lunch: the capital waits at the end of the term behind an exit strategy you must nominate and honour, and over a five-year fix the repayment route builds £16,605 of equity for £14,557 of extra cash while paying less interest. Pick interest-only to run a business; pick repayment to buy an asset outright; or take interest-only and overpay to hold both options. Then make the tax structure match the borrowing structure — that’s the decision that outlasts every fix.
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Buy-to-let interest-only: FAQs
Are buy-to-let mortgages interest-only?
Mostly, yes — around 80% of UK buy-to-let mortgages are interest-only, making it the standard landlord structure rather than the exception it is in residential lending. You pay only the interest each month, keeping payments roughly 27% lower than repayment and cashflow strong, but the full capital remains owed at the end of the term. Repayment buy-to-let mortgages are available from most lenders for landlords who prefer to clear the debt over the term, and lenders assess both against rental cover of the interest.
Should my buy-to-let be interest-only or repayment?
It depends on the job the property does. Interest-only suits portfolio builders reinvesting cashflow, higher-rate taxpayers managing Section 24 through company structures, and anyone valuing flexibility — on a £150,000 loan at 5.25%, it frees £242.62 a month versus 25-year repayment. Repayment suits single-property landlords aiming to own outright by retirement and strong-yield properties where rent covers the higher instalment: over a five-year fix it builds £16,605 of equity for £14,557 of extra cash. A middle path — interest-only with voluntary overpayments — captures both.
How much can I borrow on an interest-only buy-to-let?
It’s set by your rent, not your salary. Lenders require rent to cover the interest by 125% (basic-rate and limited-company borrowers) to 145% (higher-rate taxpayers) at a stress rate — near pay-rate on five-year fixes, typically pay-rate plus around 2% on shorter deals. Illustratively, £900 monthly rent supports between £102,735 (145% at a 7.25% stress) and £164,571 (125% at a 5.25% pay-rate) — a spread of over £60,000 from tax band and product choice alone. Most lenders also want a 20–25% deposit.
What happens at the end of an interest-only buy-to-let mortgage?
The full original capital falls due — borrow £150,000 and you owe £150,000. Lenders require a nominated exit strategy at application: refinancing onto a new deal (the route most landlords roll through fix after fix), selling the property and repaying from proceeds (remembering capital gains tax), or repaying from savings and investments, with evidence. Mixing strategies is acceptable. The practical risk isn’t the structure — it’s drift: landlords who never chose an end-game reach later life with a balance lenders are less willing to keep rolling.
Why do landlords prefer interest-only mortgages?
Three structural reasons. Cashflow: the lower payment turns a break-even property into one producing a monthly surplus that absorbs voids, maintenance and fees — or funds the next deposit. Lending design: buy-to-let affordability is tested on rental cover of the interest, so the product and the assessment fit together. Flexibility: most deals allow around 10% annual overpayment without penalty, so landlords can repay capital by choice in good months rather than by obligation in bad ones. The price is that nothing amortises automatically — the exit strategy does the work repayment would have done.
Does Section 24 make interest-only worse for landlords?
For higher-rate personal landlords, it sharpens the cost. Interest-only maximises your interest bill, and Section 24 restricts personal relief on that interest to a flat 20% credit — so a 40% taxpayer is taxed on income that funds a mortgage credited back at half their rate, and the bigger the interest, the wider the gap. Basic-rate landlords within their band are broadly unaffected, and limited companies escape entirely, deducting interest in full against corporation tax. That’s why the interest-only decision and the personal-versus-company decision belong together, with a qualified tax adviser involved.
- UK Finance — Buy-to-Let Lending data (Q1 2026 average rates, ICR, arrears)
- Moneyfacts — Buy-to-Let Mortgage Rates (current market averages)
- MoneyHelper — free, government-backed money guidance
Important information
nextmove is an introducer, not a lender or adviser. This article is for general information only and does not constitute financial or tax advice. Worked figures are illustrative: the 5.25% rate is a mid-market illustration and your actual rate, ICR requirement, stress rate and maximum borrowing depend on your circumstances and lender criteria, which change. Interest-only borrowing requires a credible repayment strategy, and failing to repay the capital at the end of the term puts the property at risk. Section 24, incorporation and disposal decisions have significant tax consequences, including capital gains tax — speak to a qualified tax adviser before structuring or restructuring. We introduce you to FCA-regulated, whole-of-market mortgage brokers who can advise on the lending side, and we may receive a fee or commission for doing so. Much buy-to-let lending is not regulated by the FCA.
Your property may be repossessed if you do not keep up repayments on your mortgage.
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