Buy-to-Let Mortgages: ICR, Deposits and Lender Criteria
Updated: 12 May 2026
How They Work and What Lenders Look For
Buy-to-let mortgages explained for UK landlords: this guide covers how lenders assess rental income, the interest coverage ratio (ICR) stress test framework the Prudential Regulation Authority expects firms to apply, deposit and loan-to-value norms, the differences between personal-name and limited company borrowing, portfolio landlord rules, and how Mortgage One can help match a case to the right lender. Buy-to-let lending is more criteria-driven than residential lending. The borrower profile, property type, ownership structure and ICR maths all change which lenders will actually offer terms.
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For an initial discussion about a buy-to-let purchase, remortgage or portfolio review, call 01202 155992 or contact Mortgage One.
What Is a Buy-to-Let Mortgage?
A buy-to-let mortgage is a mortgage for a property you intend to let to tenants rather than live in yourself. That could mean buying your first investment property, remortgaging an existing rental, switching a previously lived-in property onto a more suitable arrangement, or expanding an existing portfolio.
If you are switching an existing property from residential use to rental, the right route may be consent to let or a remortgage, depending on your lender and your plans. If you are remortgaging an existing rental or reviewing your refinance options, see our remortgaging guide.
How Buy-to-Let Differs From Residential Lending
Buy-to-let lending works differently from owner-occupied lending in a few key areas.
• Deposit. Many buy-to-let cases are geared around a maximum of 75% loan-to-value, so a 25% deposit or equivalent equity is common. Some lenders accept 20% on selected products and a small number will consider 15% in particular cases, with criteria.
• Affordability. Lenders usually assess the expected rent against a stressed mortgage payment using an interest coverage ratio (ICR), rather than relying only on salary multiples.
• Repayment basis. Many buy-to-let mortgages are arranged on an interest-only basis, although capital repayment is also available.
• Pricing and fees. Buy-to-let rates and fees are often different from standard residential products, with product fees frequently higher.
• Property use. The way the property will be let matters. Standard single-let property, HMO, multi-unit property and holiday let cases all sit in different parts of the market. If the property will be used for short-term holiday letting, read our holiday let mortgage guide.
Who Buy-to-Let Mortgages Can Suit
This page is written for:
• first-time landlords
• existing landlords buying again
• borrowers remortgaging a let property
• accidental landlords who need to regularise the mortgage position
• landlords considering a limited company or SPV structure
• houses in multiple occupation (HMO) properties
• portfolio landlords with several mortgaged properties
Some lenders are more comfortable where the applicant already owns their own home and has separate earned income outside the rent. Others are more flexible, but lender choice depends heavily on the detail of the case.
What Lenders Look At
When assessing a buy-to-let case, lenders usually look at the full picture rather than just the property value.
• Deposit or equity position
• Expected rental income
• Personal income and overall affordability
• Credit history and existing commitments
• Property type and tenancy type
• Landlord experience
• Ownership structure, including personal name or limited company
• Portfolio size if you already hold other mortgaged rentals
Some lenders also apply minimum income rules, and some prefer applicants who already own a residential property. Before applying, it is sensible to download your credit report and review any issues early.
Deposit, Loan-to-Value and Borrowing
For many mainstream buy-to-let cases, the conversation starts around loan-to-value. A lower LTV can improve product choice and may help with pricing, while higher LTV cases can become narrower and more criteria-sensitive. Borrowing is then assessed against the projected or actual rent, not just against your income in the same way as a residential case.
In practical terms, the stronger the deposit, rent, credit profile and property type, the more options you are likely to have. That does not mean the cheapest headline rate is always the right fit. Fees, stress testing, early repayment charges, valuation approach and lender appetite all matter.
How Lenders Assess Affordability: The ICR Stress Test
Buy-to-let affordability is usually assessed through rental coverage. The Prudential Regulation Authority expects firms to assess whether rental income is sufficient to support the interest cost, with a typical minimum interest coverage ratio of 125% and interest rate stress testing of at least 5.5% in certain cases, with particular attention to portfolio landlords. In practice, individual lenders frequently apply higher ICR thresholds, often 145% for higher-rate taxpayers and 160% to 175% for additional-rate taxpayers, HMO cases and limited companies, with rates varying by lender.
Worked example. Take a higher-rate taxpayer applying for a £200,000 interest-only buy-to-let mortgage at a 5.5% stress rate with a 145% ICR. The stressed annual interest cost is £200,000 × 5.5% = £11,000. Applying the 145% ICR multiplier gives a required gross annual rent of £11,000 × 1.45 = £15,950, or £1,329 per month. If the property realistically rents at £1,329 or above, the case clears that lender’s ICR test. If it rents at £1,200, the same lender would either reduce the loan size, decline the case or look at it on a 125% ICR product, where applicable. The same case at a different lender stressing at 5.5% with 125% ICR would require gross monthly rent of £1,146, materially expanding the workable loan size.
That is why two landlords buying similar properties can receive very different outcomes. The lender may treat taxpayer status, ownership structure, fixed rate length, portfolio size, property type and background commitments differently, even where the rent and deposit look identical.
To work through the ICR maths against a specific property, deposit and lender shortlist, call 01202 155992 or contact Mortgage One.
Interest-Only or Capital Repayment
Many buy-to-let mortgages are interest-only, which keeps monthly payments lower because you are only paying the interest during the term. Capital repayment is also available and may suit some landlords who want to reduce the balance over time. The right structure depends on your cash flow, long-term plan and exit strategy. If you choose interest-only, you need a credible plan for repaying the capital at the end of the term, whether that is property sale, refinance, savings or other assets.
Limited Company Buy-to-Let
For some landlords, buying or remortgaging through a limited company can be worth exploring. In mortgage terms, this is a specialist area with different lender criteria, different documentation requirements and often different pricing from personal-name borrowing. Some lenders prefer a straightforward special purpose vehicle with a clean property-letting purpose. If you are considering this route, read our limited company buy-to-let guide.
Whether a limited company is the right route is not just a mortgage question. Tax treatment varies according to individual circumstances and is subject to change, so you should speak to a qualified accountant before deciding on the ownership structure.
Portfolio Landlords and More Complex Cases
If you already have four or more distinct mortgaged buy-to-let properties in aggregate, lenders are likely to treat you as a portfolio landlord under the Prudential Regulation Authority framework. At that point, underwriting becomes more detailed. The lender may want a full property schedule, current balances, rental figures, asset and liability information, portfolio cash flow and a clearer explanation of how the portfolio is managed.
This is where broker-led packaging becomes much more valuable. A case can look strong on one property but still fail if the wider portfolio does not fit the lender’s model. For deeper detail, see our portfolio landlord guide.
Costs and Landlord Responsibilities
The mortgage is only one part of the budget. Other costs can include valuation fees, legal costs, lender fees, broker fees where charged, insurance, repairs, furnishing, letting costs and contingency for void periods.
Stamp Duty Land Tax is also important. In England and Northern Ireland, purchases of additional residential property usually attract the higher SDLT rates, although the exact outcome depends on your circumstances. Use our stamp duty calculator for an initial estimate, then confirm the final figure with your solicitor.
You also need to understand the practical responsibilities of being a landlord. GOV.UK sets out the rules that landlords must follow, including keeping rented properties safe and free from health hazards, protecting deposits where required, providing an Energy Performance Certificate, ensuring gas and electrical safety and complying with right to rent checks in England. HMO and local licensing rules can also apply depending on the property and area, so confirm the position with your local authority or solicitor.
Documents and Application Process
The exact paperwork varies by lender and by case type, but landlords are commonly asked for:
• proof of identity and address
• proof of income
• bank statements
• evidence of deposit or equity
• current mortgage statement if remortgaging
• expected rental assessment or tenancy evidence
• details of other properties owned
• company documents if buying through a limited company
For more detail on the wider mortgage process, see our mortgage application guide.
A typical process looks like this:
• initial fact-find and lender research
• decision in principle where appropriate
• property and rental review
• full application
• valuation and underwriting
• mortgage offer
• conveyancing and completion
Speaking to a Buy-to-Let Mortgage Broker
A specialist buy-to-let mortgage broker matters more on BTL cases than on a typical residential mortgage because the lender criteria are wider, the ICR maths cuts loan size before headline rate does, and the right lender for a single-let in personal name is rarely the right lender for an HMO held in a limited company.
A buy-to-let broker can:
• match the case to lenders whose ICR thresholds, stress rates and tax-status treatment actually fit, before any application is submitted
• test the loan size at multiple ICR and stress-rate combinations to find the structure that supports the borrowing required
• package portfolio cases against lender models that accept the wider exposure, particularly where the portfolio mixes personal-name and limited company holdings
• flag where a 5-year fixed rate would let the lender use a lower stress rate and increase the workable loan size
• handle HMO, holiday let, multi-unit freehold block and non-standard construction cases where mainstream BTL lenders will not engage
Mortgage One has whole of market access for buy-to-let lending. Whether you are buying your first rental, remortgaging an existing let property, reviewing a limited company structure or expanding a portfolio, the work is in matching the case to lenders whose criteria fit the detail.
To structure a buy-to-let application against the right lender from the outset, call 01202 155992 or contact Mortgage One.
The information provided in this article is for general guidance only and does not constitute personal or regulated financial advice. If you’d like to understand what these moves could mean for you, speak to Mortgage One. We can explain your options and timings based on your specific circumstances.
Some Buy to Let mortgages are not regulated by the Financial Conduct Authority.
FAQs
1. How are buy-to-let mortgages explained in simple terms? A buy-to-let mortgage is borrowing secured against a property you intend to rent out rather than live in. Lenders assess the case on the expected rent, the deposit, the property type and your overall profile. Affordability is measured through an interest coverage ratio against a stressed interest rate, rather than primarily through salary multiples as a residential mortgage would be.
2. Can first-time landlords get a buy-to-let mortgage? Yes. Some lenders will consider first-time landlords, although criteria can be tighter and lender choice is narrower. Deposit size, personal income, credit profile, property type and whether you already own a home can all affect the options available.
3. How much deposit do I need for a buy-to-let mortgage? Many buy-to-let cases are geared around up to 75% loan-to-value, which means a 25% deposit or equivalent equity is common. Some lenders accept 20% on selected products, with a small number considering 15% in particular cases. The exact requirement depends on the lender, the property and your overall profile.
4. How do lenders assess buy-to-let affordability? Lenders assess the expected rental income against a stressed mortgage payment using an interest coverage ratio (ICR). The PRA framework sets a baseline of 125% ICR with a stress rate of at least 5.5% in certain cases. Individual lenders frequently apply higher thresholds, typically 145% for higher-rate taxpayers and 160% to 175% for additional-rate taxpayers, HMO cases or limited companies.
5. Are buy-to-let mortgages interest-only or capital repayment? Many buy-to-let mortgages are interest-only, but capital repayment options also exist. The right structure depends on your objectives, monthly budget and how you plan to repay the balance if you choose interest-only.
6. What are the disadvantages of a buy-to-let mortgage? Buy-to-let mortgages typically require larger deposits than residential mortgages, often 25% or more. Product fees are frequently higher and rates can be higher than equivalent residential products. The borrowing is also subject to ICR stress testing, which can cut the workable loan size below what the property might appear to support on simple rent-to-mortgage maths. Many buy-to-let mortgages are not FCA regulated, and the wider landlord position carries its own costs, void risk and tax considerations.
7. Can I get a buy-to-let mortgage through a limited company? Yes, in principle. Many landlords use a limited company or special purpose vehicle, but lender criteria, documentation and personal guarantee requirements can differ from personal-name borrowing. Mortgage advice and tax advice are separate, so you should also speak to a qualified accountant on the tax position before deciding on the structure.
8. What is a portfolio landlord? A portfolio landlord is generally a landlord with four or more distinct mortgaged buy-to-let properties in aggregate. Once a case falls into portfolio lending under the PRA framework, the lender assesses the wider portfolio as well as the specific property being bought or remortgaged.
9. Do I pay higher Stamp Duty on a buy-to-let purchase? Usually, purchases of additional residential property in England and Northern Ireland attract higher Stamp Duty Land Tax rates, although the exact outcome can depend on your circumstances. Always confirm the final figure with your solicitor.
10. Are buy-to-let mortgages regulated? Many buy-to-let mortgages are not regulated in the same way as residential mortgages. Consumer buy-to-let cases can sit under a different regulatory framework, so the position depends on why the property is being let and the circumstances of the case.