Buy-to-Let Mortgages 2026/27: How They Work, the Rental Stress Test and Costs

How UK buy-to-let mortgages work in 2026/27 - interest-only, ~25% deposit, the rental stress test (ICR 125% / 145%), 5% SDLT surcharge and company vs personal.

2026/27 tax year

Property & Landlord
UK-wide

A plain-English guide for UK landlords and would-be landlords on how buy-to-let (BTL) mortgages work in 2026/27. BTL mortgages are usually interest-only, need a larger deposit (typically around 25%, sometimes 40% for the sharpest rates) and are assessed mainly on expected rental income, not your salary. We cover the rental stress test (ICR 125% basic-rate / 145% higher-rate at a stressed rate around 5.5%), deposit and costs including the 5% additional-property SDLT surcharge, personal name vs limited company, regulated vs unregulated lending, portfolio landlords, and why a specialist broker helps. For the landlord tax detail, we cross-link the dedicated guides rather than repeat it here.

How does a buy-to-let mortgage work in 2026/27?

A buy-to-let (BTL) mortgage is a loan to buy a property you intend to rent out. It usually differs from a residential mortgage in three ways: it is normally interest-only (you pay just the interest each month and repay the capital at the end), it needs a larger deposit (typically around 25%, and sometimes 40% for the best rates), and affordability is assessed mainly on the expected rental income rather than your salary. Lenders apply a rental stress test - the rent must typically cover 125% of the mortgage interest for basic-rate taxpayers and 145% for higher-rate taxpayers, calculated at a stressed interest rate (commonly around 5.5%). Most BTL lending is not FCA regulated, but "consumer buy-to-let" (for example accidental landlords) is regulated. Rates and fees are generally higher than on residential mortgages, and buying an additional property adds a 5% SDLT surcharge in England and Northern Ireland.

2026/27 buy-to-let mortgage at a glance

Typical deposit

~25%

Around 75% LTV max; ~40% deposit for the best rates

Rental stress test

125% / 145%

Basic / higher-rate ICR at a stressed rate ~5.5%

Additional-property SDLT

+5%

England + NI surcharge since 31 Oct 2024

Figures are typical market conventions, not fixed law - individual lenders set their own deposit, ICR and stressed-rate policies. Sources: MoneyHelper, PRA SS13/16 and GOV.UK (see the Sources list below).

1. How a buy-to-let mortgage works

A buy-to-let mortgage is a loan for a property you plan to rent out rather than live in. Three features usually set it apart from a residential mortgage:

Usually interest-only. Most BTL mortgages are interest-only, so the monthly payment covers only the interest and you repay the capital at the end of the term (for example by selling or refinancing). Payments are lower month to month, but the debt does not shrink - MoneyHelper notes most buy-to-let mortgages are interest-only.
Larger deposit. Lenders typically look for a deposit of at least around 25% (up to ~75% LTV), and often around 40% (60% LTV) for the lowest rates. The bigger your equity, the wider your choice of deals.
Assessed on rent, not salary. The amount you can borrow is based mainly on the rent the property earns or is expected to earn, not on your personal income. Lenders still run background checks (many want a minimum personal income), but the rental figure drives the loan size.

Rental profit is taxable - report it through Self Assessment. See our complete landlord tax guide for 2026/27 for how the numbers flow through to your tax bill.

2. The rental stress test (ICR)

The rental stress test is the single most important hurdle in a buy-to-let application. Lenders apply an Interest Coverage Ratio (ICR): the rent must exceed the mortgage interest by a set margin. This comes from the Prudential Regulation Authority's underwriting standards, Supervisory Statement SS13/16, which require lenders to test affordability robustly against future interest-rate rises and the borrower's tax costs.

125% for basic-rate taxpayers - rent must cover at least 125% of the mortgage interest.
145% for higher-rate taxpayers - a bigger margin, reflecting the extra tax higher earners pay on rental profit (linked to the Section 24 finance-cost restriction).
Stressed interest rate. The interest figure is calculated at a notional stressed rate - commonly around 5.5%, or the pay rate plus a margin - not today's actual rate, so the test checks the rent would still cover the mortgage if rates climbed.

Worked example: if the stressed monthly interest is £1,000, a basic-rate landlord would typically need about £1,250 a month in rent (125%), and a higher-rate landlord about £1,450 (145%). If the rent does not comfortably beat the stressed interest by the required margin, the lender caps or declines the loan. Exact ratios and stressed rates vary by lender and by product, so treat 125%/145% and ~5.5% as common conventions rather than fixed rules. Some lenders offer "top-slicing", using surplus personal income to help bridge a shortfall.

3. Deposit and upfront costs

Buy-to-let carries more upfront cost than a residential purchase. Budget for:

Deposit - typically at least around 25% of the price, and often around 40% for the best rates.
Product / arrangement fee - buy-to-let fees are often higher than residential, and are sometimes charged as a percentage of the loan, so a low headline rate can still be expensive overall. Compare the total cost over the fixed period, not just the rate.
Higher interest rates - lenders generally price BTL above residential deals because rented property is seen as higher risk (void periods, arrears) and most BTL lending sits outside FCA regulation.
SDLT additional-property surcharge - in England and Northern Ireland, buying an additional residential property adds a 5% surcharge on top of the standard Stamp Duty Land Tax rates. This rose from 3% to 5% for transactions completing on or after 31 October 2024 (Autumn Budget 2024). Scotland (LBTT) and Wales (LTT) run their own systems with their own additional-property surcharges.
Valuation, legal and (if used) broker fees, plus ongoing running costs - letting/management, insurance, maintenance, safety certificates and empty periods.

4. Personal name vs limited company

You can hold a buy-to-let in your own name or through a limited company - usually a special purpose vehicle (SPV) set up just to hold property. Many landlords now use a company largely because of the Section 24 mortgage-interest restriction: individual landlords can no longer deduct finance costs from rental income and instead receive only a 20% basic-rate tax credit, whereas a company generally deducts its full finance costs before Corporation Tax.

Company buy-to-let mortgages are widely available, but the lender pool is narrower and rates and fees are often higher than personal-name lending. Incorporating is not automatically better - it depends on your income, portfolio size, how much profit you draw out and your longer-term plans, and there are set-up and running costs. We keep the tax detail light here and cross-link the dedicated guides:

Section 24 mortgage-interest restriction, detailed 2026/27 guide - how the finance-cost restriction and 20% tax credit work.
Landlord limited-company incorporation guide 2026/27 - whether an SPV makes sense, and the costs and trade-offs.

Take professional tax and mortgage advice before choosing an ownership structure - moving a personal property into a company is itself a sale, which can trigger SDLT and Capital Gains Tax.

5. Regulated vs unregulated, and portfolio landlords

Most buy-to-let mortgages are not FCA regulated, because they are treated as business lending taken out for investment. The main exception is consumer buy-to-let (CBTL), which is regulated. A CBTL contract broadly covers borrowers who did not take on the mortgage wholly or predominantly for business - for example an "accidental landlord" letting out an inherited property or a former home, or someone letting to a close family member. CBTL sits under the Mortgage Credit Directive Order 2015 (SI 2015/910), and firms must be registered with or authorised by the FCA, giving borrowers protections closer to a residential mortgage, including access to the Financial Ombudsman Service.

Portfolio landlords face extra scrutiny. Under PRA standards (SS13/16), a portfolio landlord is anyone with 4 or more mortgaged buy-to-let properties, counted across all lenders. At that point lenders must apply more detailed, specialist underwriting across the whole portfolio - assessing aggregate borrowing, overall loan-to-value and rental cover on every mortgaged property, usually via a portfolio questionnaire and a business plan. Fewer lenders operate in this space and applications take more packaging.

6. How to apply and why a specialist broker helps

A typical application runs: decision in principle, full application with the property's rental figures and (for companies) SPV details, a lender valuation that also confirms the achievable rent, the ICR stress test, then formal offer and completion. A specialist broker is often worth using, particularly for limited-company lending or portfolio landlords, because:

Whole-of-market access. Much of the buy-to-let market is intermediary-only, so a broker can reach lenders and products you cannot approach directly.
Matching the stress test. A broker can steer you to lenders whose ICR and stressed-rate policy fits your rent level and tax position - the difference between a loan that passes and one that is capped.
Portfolio packaging. For 4+ mortgaged properties, a broker collates the property schedule, rents and business plan to meet the PRA's specialist underwriting.

This guide is general information, not mortgage advice. Your lender and product choice should be based on advice tailored to your circumstances, and we do not recommend specific lenders or brokers.

Buy-to-let landlord complete guide 2026/27 - rental income, allowable expenses and how landlord tax works.
Section 24 mortgage-interest restriction, detailed 2026/27 guide - the finance-cost restriction that drives many company purchases.
Landlord limited-company incorporation guide 2026/27 - whether to hold buy-to-lets in an SPV.
Self-employed and contractor mortgage guide 2026/27 - how lenders assess self-employed income for a mortgage.

Frequently asked questions

How much deposit do I need for a buy-to-let mortgage?

Most buy-to-let lenders want a deposit of at least around 25% of the property price - in other words a maximum loan-to-value (LTV) of about 75% - according to MoneyHelper. Many of the lowest advertised rates require a larger deposit still, often around 40% (60% LTV), because a bigger equity cushion reduces the lender's risk. The exact figure varies by lender, property type and your circumstances, and specialist or new-build lending can require more. Your deposit is separate from the other upfront costs: the arrangement/product fee, valuation and legal fees, and the Stamp Duty Land Tax additional-property surcharge of 5% (in England and Northern Ireland, on top of the standard SDLT rates). Treat 25% as a realistic minimum to budget for, not a guaranteed entry point.

How is buy-to-let affordability calculated?

Buy-to-let affordability is assessed mainly on the property's expected rental income, not your salary. Lenders apply an Interest Coverage Ratio (ICR) rental stress test that flows from the Prudential Regulation Authority's underwriting standards (Supervisory Statement SS13/16). Typically the rent must cover at least 125% of the mortgage interest for a basic-rate taxpayer (and for most limited-company borrowers) and around 145% for a higher-rate taxpayer, reflecting the tax landlords pay on rental profit. The calculation uses a stressed interest rate - commonly around 5.5%, or the pay rate plus a margin - rather than today's actual rate, so it tests whether the rent would still cover the mortgage if rates rose. For example, if the stressed monthly interest is £1,000, a higher-rate landlord would typically need about £1,450 a month in rent to pass. Exact ratios and stressed rates vary by lender, so treat 125%/145% and 5.5% as common market conventions rather than fixed rules.

Can I get a buy-to-let mortgage through a limited company?

Yes. Many landlords now buy through a limited company, usually a special purpose vehicle (SPV) set up just to hold property. A big driver is the Section 24 mortgage-interest restriction: individual landlords can no longer deduct finance costs (like mortgage interest) from rental income and instead get only a 20% basic-rate tax credit, whereas a company can generally deduct its full finance costs as a business expense before Corporation Tax. Company buy-to-let mortgages are widely available, though the range of lenders can be narrower and rates and fees are often higher than personal-name lending. Incorporating is not automatically better - it depends on your income, portfolio size, how much you draw out and future plans, and there are set-up and running costs. See our landlord limited-company incorporation guide and Section 24 guide for the tax detail, and take professional advice before deciding.

Are buy-to-let mortgages regulated by the FCA?

Most buy-to-let mortgages are not regulated by the Financial Conduct Authority, because they are treated as business lending taken out for investment purposes. However, "consumer buy-to-let" (CBTL) is regulated. A CBTL contract broadly covers people who did not take on the mortgage wholly or predominantly for business - the classic example is an "accidental landlord" who inherited a property or is letting out a former home, or someone letting to a close family member. CBTL sits under the Mortgage Credit Directive Order 2015, and firms arranging or lending on CBTL must be registered with or authorised by the FCA, giving borrowers protections closer to a residential mortgage (including access to the Financial Ombudsman Service). Whether your deal is regulated depends on the facts, so a broker will confirm which regime applies to you.

Why are buy-to-let mortgage rates higher than residential rates?

Lenders generally price buy-to-let mortgages higher than residential ones because they view rented property as higher risk: rental income can be interrupted by void periods or arrears, and the loan usually depends on the property performing rather than the borrower's salary. Buy-to-let deals also frequently carry higher arrangement or product fees, sometimes charged as a percentage of the loan rather than a flat amount, which can make a headline low rate more expensive overall. Because most buy-to-let lending is not FCA regulated, the products sit in a different, more commercially priced part of the market. When comparing deals, look at the true cost over the fixed period (rate plus fees), not just the advertised rate, and remember the mortgage is normally interest-only so the monthly payment does not reduce the capital you owe.

What is a portfolio landlord and does it change the mortgage?

Under the Prudential Regulation Authority's standards (SS13/16), a portfolio landlord is someone with four or more mortgaged buy-to-let properties, counted across all lenders. Once you reach that threshold, lenders must apply more detailed, specialist underwriting that looks at your whole portfolio - not just the single property you are buying or remortgaging. In practice that means assessing your aggregate borrowing, overall loan-to-value and rental cover across every mortgaged property, and often completing a portfolio questionnaire and business plan. Because this is more involved, fewer lenders operate in the portfolio space and applications take more packaging, which is one reason experienced landlords tend to use a specialist broker. The four-property test is about mortgaged buy-to-lets; unencumbered (mortgage-free) properties you own are still relevant to the overall picture lenders assess.

What upfront costs come with a buy-to-let purchase?

Beyond the deposit (typically at least around 25% of the price), budget for: the lender's arrangement or product fee (sometimes a percentage of the loan); a valuation fee; conveyancing and legal fees; and any broker fee. The biggest one-off cost is usually Stamp Duty Land Tax. In England and Northern Ireland, buying an additional residential property carries a 5% surcharge on top of the standard SDLT rates (the surcharge rose from 3% to 5% for transactions completing on or after 31 October 2024, per Autumn Budget 2024). Scotland and Wales run their own systems (Land and Buildings Transaction Tax and Land Transaction Tax) with their own additional-property surcharges. On top of purchase costs, factor in ongoing running costs - letting/management fees, insurance, maintenance, safety certificates and periods when the property is empty - when working out whether the rent will comfortably cover the mortgage.

Should I use a specialist buy-to-let mortgage broker?

A specialist broker is often worth using for buy-to-let, especially for limited-company (SPV) lending or if you are a portfolio landlord. Much of the buy-to-let market is not FCA regulated and a large share of competitive deals are only available through intermediaries rather than direct to borrowers, so a whole-of-market broker can search lenders you cannot approach yourself. They also help package a portfolio application - collating property schedules, rental figures and a business plan - to meet the PRA's specialist underwriting requirements, and can match you to lenders whose rental stress test (ICR) works for your rents and tax position. This guide is general information, not mortgage advice: your lender and product choice should be based on advice tailored to your circumstances. We do not recommend specific lenders or brokers.