A calm first check · on your device
Will this buy-to-let pass the lender's stress test?
Before you offer on a buy-to-let, the lender doesn't ask what you earn — it asks whether the rent covers the mortgage at a stressed interest rate. This checks that in a few seconds, so you know roughly how much you could borrow, or whether a deal stacks up, before you go any further. It runs on your device; the figures you enter aren't sent to us or stored.
Generic information, not a personal recommendation. This is an indicative check to help you prepare — it is not a mortgage offer, a lending decision, or advice about your own borrowing. Arranging a mortgage, and any regulated advice, is done by an appropriately authorised broker — not by this tool. Every lender sets its own criteria, so a real figure will differ. When you’re ready, we can introduce you to Broker’s Choice Limited t/a BCL Commercial Finance, which arranges commercial finance and is not FCA-regulated; we’ll always tell you when we make an introduction.
Check a deal
About the default figures. The coverage ratios (125% / 145% / 165%) and the 5.5% stress rate used here are typical market defaults, not any single lender’s criteria. Real lenders vary these constantly — by product, property type, tax status and month. These defaults are indicative and pending confirmation against current lender criteria; treat the result as a rough guide only, and verify with a broker before you rely on it. (Defaults reviewed September 2026.)
A worked example
Illustrative only.
Sarah is a higher-rate taxpayer buying a £250,000 flat that will rent for £1,300 a month. She wants a 75% loan — £187,500. As a higher-rate taxpayer, the lender needs the rent to cover the interest by 145%, stressed at 5.5%.
Required rent = £187,500 × 5.5% × 145% ÷ 12 = £1,246 a month. Sarah’s £1,300 clears it — so the deal passes, with a little room to spare. If she bought through a limited company (125% cover), the same loan would need only about £1,074 rent — so she could borrow more against the same flat, one reason higher-rate landlords often look at company structures.
How the lender's stress test works
A buy-to-let mortgage is assessed on the property's rent, not your salary. The lender takes a “stress” interest rate (higher than the rate you’ll actually pay — usually 5.5% in 2026), works out the interest on your loan at that rate, and checks the rent covers it by a set margin. That margin is the Interest Cover Ratio (ICR): 125% for a basic-rate taxpayer or limited company, 145% for a higher-rate taxpayer, and up to about 165% for additional-rate. This framework comes from the Prudential Regulation Authority’s Supervisory Statement SS13/16.
In plain terms: the rent has to be 25%–65% more than the stressed interest, depending on your tax position. That’s why a higher-rate landlord can borrow less against the same rent than a basic-rate one — and why many higher-rate landlords look at holding through a company.
Common questions
How much can I borrow on a buy-to-let?
Roughly, the maximum loan is: (monthly rent × 12) ÷ (stress rate × ICR). So on £1,500 rent, a 5.5% stress rate and a 125% ICR, that’s about £261,800; at 145% it drops to about £225,700. The rent is doing the work, not your income.
Why do higher-rate taxpayers get a stricter test?
Because Section 24 leaves higher-rate landlords with less after-tax rent to service the debt. Since mortgage interest is no longer deducted from profit (you get a 20% credit instead), lenders require a bigger buffer — 145% instead of 125%.
What is a stress rate?
A stress rate is a higher, hypothetical interest rate the lender tests you against — typically 5.5% in 2026 — even if your actual product rate is lower. It checks the property could still cover its mortgage if rates rose. Five-year fixes often get a lower stress rate, which can push a marginal deal through. Individual lenders set their own stress rate — often the higher of a fixed floor (around 5.5%) or your product rate plus a margin — so treat the figure here as a typical guide.
Can I borrow more than the rent alone supports?
Sometimes — through “top-slicing”. Some lenders will let you use surplus personal or other income to top up a marginal case where the rent alone doesn’t quite pass the ICR test. Not all lenders offer it, and the rules vary, so it’s one of the things a specialist broker checks for you. This calculator shows the rent-only position.
What changes at four properties?
Once you hold four or more mortgaged buy-to-lets you’re a “portfolio landlord”, and lenders assess your whole portfolio, not just the new property. Fewer lenders will look at you and the paperwork increases — this is exactly where a specialist broker earns their fee.
Important — please read
- This is a guide, not a quote or a decision. The figures are indicative estimates based on typical market defaults, not the criteria of any particular lender, and not a mortgage offer or an assessment of your circumstances.
- Not advice. Nothing here is financial, mortgage, tax or legal advice, or a personal recommendation. Arranging a mortgage and giving regulated advice is done by an appropriately authorised firm — not by this tool or by Landlord Tax Enquiry.
- Lender criteria vary and change. Coverage ratios, stress rates, top-slicing and portfolio rules differ between lenders and are updated frequently. Your actual borrowing figure may be higher or lower than shown.
- Introducer, not lender or FCA-regulated adviser. Where finance is involved we may introduce you to Broker’s Choice Limited t/a BCL Commercial Finance, which arranges commercial finance and is not FCA-regulated. We’ll always tell you when we make an introduction.
- Always verify before you rely on it. Confirm any figure with a qualified broker who can check live lender criteria for your situation before you offer on a property or commit to borrowing.
Figures and default assumptions reviewed September 2026; lender criteria and rates can change at any time.
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