Buy-to-let mortgage (BTL)
A buy-to-let mortgage is a specialist loan product designed for the purchase or remortgage of a residential property that will be let to tenants rather than occupied by the borrower. According to MoneyHelper, lenders assess BTL mortgage applications primarily on expected rental income rather than the applicant's salary, the core feature that distinguishes them from standard residential mortgages. BTL mortgages have been available in the UK since 1996 and form the principal financing instrument for landlords in the private rented sector. The broader investment model is defined separately, see buy-to-let.
How a buy-to-let mortgage differs from a residential mortgage
Three features separate a BTL mortgage from a standard owner-occupier loan:
Lending basis. Lenders assess how much to lend primarily by reference to the expected rental income rather than the borrower's personal salary. The rent must typically cover mortgage interest by a specified margin, known as the interest coverage ratio (ICR). Most lenders apply an ICR of 125%–145% at a stressed interest rate (commonly 5.5%–7%), meaning the monthly rent must exceed the stressed monthly interest payment by that proportion. Lenders may also "top-slice" an application using personal income where rental income alone falls short.
Deposit requirements. A minimum deposit of 25% of the property value is standard for a BTL mortgage. Some lenders accept 20% for lower-risk applications; portfolio landlords and those with adverse credit may be required to put down 30–40%. Higher loan-to-value (LTV) products carry higher interest rates and tighter ICR requirements. August's buy-to-let mortgage calculator lets you model scenarios across different LTV bands, run ICR stress tests, and compare the effective cost of interest-only and repayment products.
Interest-only terms. The majority of BTL mortgages are offered on an interest-only basis. The landlord pays only the interest each month and must repay the full capital, typically by sale, remortgage, or other investment, at the end of the mortgage term. This structure lowers monthly outgoings relative to a repayment mortgage, which is why most lenders assess BTL affordability on the interest-only payment, not a capital-and-interest figure.
Eligibility criteria
Lender criteria vary, but the typical requirements for a standard BTL mortgage in the UK are:
A minimum personal income of £25,000 per year (especially for first-time landlords, though some lenders waive this for experienced investors)
Existing homeownership (some lenders require this; others do not)
Minimum age of 21 at application (some lenders set 18)
A maximum age at mortgage end of 70–85, depending on lender
A satisfactory credit history
A property value above a minimum threshold (typically £50,000–£75,000)
Landlords with four or more mortgaged buy-to-let properties are classified as portfolio landlords under PRA guidance introduced in 2017. Portfolio landlords face additional underwriting scrutiny, including assessment of their entire portfolio's aggregate ICR, not just the subject property.
Consumer buy-to-let
Not all BTL mortgages are treated as commercial products. A consumer buy-to-let mortgage applies where the borrower is not acting wholly or predominantly for business purposes, for example, a landlord who has inherited a property or is letting out a former home following a change in circumstances. Consumer BTL mortgages are regulated by the Financial Conduct Authority under the Mortgage Credit Directive Order 2016 and carry additional borrower protections. Standard BTL mortgages remain unregulated.
What happens to a tenant if a landlord defaults
From a tenant's perspective, the existence of a BTL mortgage does not reduce statutory rights. If a landlord falls behind on mortgage payments and the lender seeks possession through the courts, the outcome depends on the terms of the specific mortgage and the type of tenancy. Under the Mortgage Repossessions (Protection of Tenants etc) Act 2010, tenants in certain circumstances can apply to the court to postpone a possession order, and some lenders are required to give tenants prior notice. A tenant cannot be evicted simply because the landlord has financial difficulties, proper court procedures must be followed in all cases.
From working with self-managing landlords across the UK, we know that many are unaware their mortgage terms place conditions on the tenancy, including restrictions on letting to tenants receiving housing benefit, or on tenancy length. It is worth checking your BTL mortgage offer carefully before granting any tenancy.
Landlords who already hold a BTL mortgage and want to switch product or release equity should also read the entry on remortgaging a rental property. For a practical guide to rates, lender criteria, and how to compare products in 2026, see August's buy-to-let mortgage guide for landlords.
Frequently asked questions
Can a first-time buyer get a buy-to-let mortgage?
Most lenders require applicants to be existing homeowners, making BTL mortgages difficult to obtain as a first-time buyer. A small number of specialist lenders offer first-time buyer BTL products, typically at higher rates and with stricter ICR requirements. First-time buyers should expect closer scrutiny of their personal financial position.
What is the interest coverage ratio (ICR)?
The ICR is the ratio of a property's expected monthly rent to the monthly interest payment on the mortgage, calculated at a stressed interest rate rather than the actual product rate. A lender requiring an ICR of 125% at a 6% stress rate means the monthly rent must be at least 1.25 times the monthly interest at 6% per annum. The ICR determines the maximum loan a lender will offer for a given rent.
Is a buy-to-let mortgage interest-only or repayment?
The majority of BTL mortgages are interest-only, meaning the capital balance does not reduce during the term. Repayment BTL mortgages are available but carry higher monthly costs and are less commonly used. Many landlords use the interest-only structure to maximise monthly cash flow while relying on property value growth or future remortgage to manage the capital balance.
Does Section 24 affect my BTL mortgage costs?
Section 24 of the Finance (No. 2) Act 2015 restricts how mortgage interest is treated for income tax purposes. Landlords who hold property in their personal name can no longer deduct BTL mortgage interest as a business expense. Instead, they receive a 20% basic-rate tax credit on their finance costs. This means the gross cost of a BTL mortgage is higher in effective tax terms for higher-rate taxpayers than it was before 2017, and it is one of the main reasons many landlords have moved to limited company structures.
The information on this page reflects UK law and lender practice as of May 2026. It is provided for general guidance only and does not constitute financial or mortgage advice. Always consult a qualified mortgage adviser before making borrowing decisions.
