Buy-to-Let Guide UK — Landlord Mortgage Basics
Planning a buy-to-let investment? Understand deposit requirements, rental yield calculations, Section 24 tax rules, and how to structure your portfolio for maximum returns.
Buy-to-let property remains one of the most popular investment strategies in the UK, with approximately 2.65 million landlords managing around 4.6 million privately rented homes according to the English Housing Survey. Despite significant tax changes in recent years — most notably the phasing out of mortgage interest tax relief under Section 24 and the 3% stamp duty surcharge on additional properties — rental property continues to offer investors a combination of monthly income and long-term capital growth that few other asset classes can match.
A buy-to-let (BTL) mortgage is a specific type of mortgage designed for properties you intend to rent out rather than live in. They work differently from residential mortgages in several important ways: the deposit requirements are higher (typically 25% minimum), the interest rates tend to be slightly above residential equivalents, and the affordability calculation is based primarily on the expected rental income rather than your personal salary. Understanding these differences is essential before committing to a purchase, because getting the structure wrong can cost you thousands in unnecessary tax or leave you unable to remortgage when your deal ends.
In this comprehensive guide, we cover everything a current or aspiring UK landlord needs to know about buy-to-let mortgages. We explain how they work, what deposit you’ll need, how lenders calculate affordability using rental coverage ratios, the tax implications you must plan for (including Section 24 and capital gains tax), the pros and cons of buying through a limited company, and the additional rules that apply if you’re a portfolio landlord with four or more mortgaged properties. We’ve also included links to our BTL calculators so you can run the numbers before making any commitments.
How buy-to-let mortgages work
A buy-to-let mortgage is specifically designed for properties you plan to rent out to tenants. Unlike a residential mortgage where affordability is based on your personal income, BTL lenders focus primarily on the expected rental income from the property — though most will also check that you have a minimum personal income (typically £25,000 per year).
The majority of BTL mortgages are interest-only, meaning your monthly payments cover only the interest on the loan. The capital balance stays the same throughout the mortgage term, and you repay it when you sell the property or through other means. This keeps monthly costs lower and maximises cash flow, which is why most landlords prefer this structure.
A buy-to-let mortgage is specifically designed for properties you plan to rent out to tenants. Unlike a residential mortgage where affordability is based on your personal income, BTL lenders focus primarily on the expected rental income from the property — though most will also check that you have a minimum personal income (typically £25,000 per year).
The majority of BTL mortgages are interest-only, meaning your monthly payments cover only the interest on the loan. The capital balance stays the same throughout the mortgage term, and you repay it when you sell the property or through other means. Use our repayment calculator to compare interest-only and repayment options.
BTL vs Residential Mortgages
| Buy-to-Let Mortgage | Residential Mortgage |
|---|---|
| Minimum 25% deposit (some lenders 20%) | Deposits from 5–10% |
| Affordability based on rental income | Affordability based on personal income |
| Most are interest-only | Mostly repayment (capital + interest) |
| Rates slightly higher than residential | Typically lower interest rates |
| Minimum personal income usually £25,000 | No minimum income requirement |
| 3% stamp duty surcharge on top of standard rates | Standard stamp duty rates apply |
Don’t use a residential mortgage for a rental
Letting out a property on a residential mortgage without your lender’s consent is a breach of your mortgage terms. If discovered, the lender can demand immediate repayment of the full loan. Always ensure you have the correct mortgage type in place before taking on tenants.
Deposit requirements and affordability
Buy-to-let deposits are significantly larger than residential ones. Most lenders require a minimum of 25% of the property’s value, giving you a maximum LTV of 75%. Some specialist lenders will go up to 80% or even 85% LTV, but rates increase noticeably at higher loan-to-value ratios.
Affordability is assessed using the rental coverage ratio (also called the interest coverage ratio or ICR). Most lenders require the expected monthly rent to be at least 125% to 145% of the monthly mortgage payment, calculated at a stressed interest rate (typically 5.5% or the pay rate plus a margin, whichever is higher).
Buy-to-let deposits are significantly larger than residential ones. Most lenders require a minimum of 25% of the property’s value, giving you a maximum LTV of 75%. Some specialist lenders will go up to 80% or even 85% LTV, but rates increase noticeably at higher loan-to-value ratios.
Affordability is assessed using the rental coverage ratio (also called the interest coverage ratio or ICR). Most lenders require the expected monthly rent to be at least 125% to 145% of the monthly mortgage payment, calculated at a stressed interest rate.
Typical BTL requirements
Lower tax bracket advantage
Some lenders use a lower rental coverage ratio (125% instead of 145%) for basic-rate taxpayers, or for properties held in a limited company. This means you may qualify for a larger mortgage — or the same mortgage on a lower rental income — depending on your tax position.
Understanding rental yield
Rental yield is the annual rental income expressed as a percentage of the property’s value. It’s the most common metric landlords use to assess whether an investment property is worthwhile. There are two types: gross yield (before expenses) and net yield (after expenses like management fees, maintenance, insurance, and void periods).
In the UK, gross rental yields typically range from around 3–4% in London and the South East to 7–9% in parts of the North West, North East, and Scotland. Higher yields often come with lower capital growth potential, so most investors aim for a balance between income and long-term appreciation.
Rental yield is the annual rental income expressed as a percentage of the property’s value. It’s the most common metric landlords use to assess whether an investment property is worthwhile. There are two types: gross yield (before expenses) and net yield (after expenses like management fees, maintenance, insurance, and void periods).
How to calculate rental yield
- 01
Find the annual rent
Multiply the monthly rent by 12. For example, if the property rents for £850 per month, your annual rent is £10,200.
- 02
Calculate gross yield
Divide the annual rent by the property value, then multiply by 100. For a £200,000 property with £10,200 annual rent: £10,200 ÷ £200,000 × 100 = 5.1% gross yield.
- 03
Deduct your annual costs
Subtract annual expenses: letting agent fees (typically 8–12% of rent), maintenance (£1,000–£2,000), insurance (£200–£400), void periods (allow 1 month), and any ground rent or service charges.
- 04
Calculate net yield
Divide your net annual income (rent minus costs) by the property value × 100. This gives you a more realistic picture of your return. Aim for a net yield of at least 3–4% to cover mortgage costs and generate profit.
Run the numbers
- BTL Maximum Mortgage CalculatorFree tool
See how much you could borrow for a buy-to-let property based on expected rental income and deposit amount.
- BTL Maximum Rent CalculatorFree tool
Work out the minimum rent you’ll need to charge to meet lender affordability requirements for your target property.
- Stamp Duty CalculatorFree tool
Calculate your total stamp duty bill including the 3% buy-to-let surcharge, so you know the true upfront cost of your investment.
Tax implications for landlords
The tax landscape for UK landlords has changed significantly since 2017. The most impactful change is Section 24 of the Finance Act 2015, which phased out the ability for individual landlords to deduct mortgage interest from their rental income before calculating tax. Instead, you now receive a basic-rate tax credit (20%) on your mortgage interest payments. This means higher-rate and additional-rate taxpayers pay considerably more tax than they did previously.
Other taxes to plan for include capital gains tax (CGT) when you sell a rental property, stamp duty land tax (SDLT) with the 3% surcharge for additional properties, and income tax on your net rental profits.
The tax landscape for UK landlords has changed significantly since 2017. The most impactful change is Section 24 of the Finance Act 2015, which phased out the ability for individual landlords to deduct mortgage interest from their rental income before calculating tax. Instead, you now receive a basic-rate tax credit (20%) on your mortgage interest payments.
This means if you’re a higher-rate (40%) or additional-rate (45%) taxpayer, you could be paying tax on rental “profits” that don’t actually exist once mortgage payments are accounted for. This has driven many landlords to explore the limited company route.
Key taxes for BTL landlords
Income Tax on Rental Profits
- Rental income is added to your other income and taxed at your marginal rate (20%, 40%, or 45%).
- You can deduct allowable expenses: letting agent fees, repairs (not improvements), insurance, and accountancy fees.
Section 24 Mortgage Interest
- Individual landlords can no longer deduct mortgage interest as an expense.
- Instead, you receive a 20% tax credit on interest payments — costing higher-rate taxpayers significantly more.
Stamp Duty Surcharge
- An additional 3% is added to every band of stamp duty when purchasing additional residential property.
- On a £250,000 BTL purchase, this adds £7,500 to your stamp duty bill.
Capital Gains Tax (CGT)
- When you sell a rental property, gains above your annual CGT allowance (£3,000 for 2024/25) are taxed at 18% (basic rate) or 24% (higher rate).
- CGT on residential property must be reported and paid within 60 days of completion.
Section 24 can push you into a higher tax band
Because your full rental income (before mortgage interest) is added to your total income, Section 24 can push basic-rate taxpayers into the higher-rate band — even if their actual cash profit is minimal. This is sometimes called the “Section 24 tax trap” and is a critical consideration for landlords with large mortgages.
Buying through a limited company
In response to Section 24, a growing number of landlords are purchasing buy-to-let properties through a Special Purpose Vehicle (SPV) limited company rather than in their personal name. A limited company can still deduct mortgage interest as a business expense, and corporation tax (currently 25% for profits over £250,000, with a small profits rate of 19% for profits under £50,000) is often lower than the combined income tax and Section 24 impact for higher-rate taxpayers.
However, the limited company route isn’t automatically better for everyone. There are additional costs including setup and accounting fees, and extracting profits from the company (via salary or dividends) creates another layer of taxation. The decision depends on your tax bracket, portfolio size, and whether you need the rental income for personal use.
In response to Section 24, a growing number of landlords are purchasing buy-to-let properties through a Special Purpose Vehicle (SPV) limited company. A limited company can still deduct mortgage interest as a business expense, and corporation tax is often lower than the combined income tax and Section 24 impact for higher-rate taxpayers.
Personal name vs Limited company
| Personal name | Limited company (SPV) |
|---|---|
| Simpler to set up and manage | Mortgage interest fully deductible against profits |
| Wider choice of mortgage products | Corporation tax at 19–25% (often lower than income tax) |
| Lower rates than limited company BTL | Easier to add business partners or plan inheritance |
| No company admin or accountancy costs | Higher mortgage rates and fees |
| Section 24 applies — mortgage interest not deductible | Additional accounting and filing obligations |
| Profits taxed at your marginal income tax rate | Extracting profits attracts dividend tax |
There’s no one-size-fits-all answer. A landlord with two properties and basic-rate tax may be better off in their personal name, while a portfolio landlord in the 40% bracket could save thousands a year through a limited company.
Portfolio landlord rules
Since September 2017, the Prudential Regulation Authority (PRA) introduced specific rules for portfolio landlords — defined as anyone with four or more mortgaged buy-to-let properties. If you fall into this category, lenders are required to apply additional scrutiny to your application, including a detailed assessment of your entire property portfolio.
This doesn’t mean you can’t get a mortgage as a portfolio landlord, but the process is more involved and the documentation requirements are greater. Working with an experienced broker is particularly valuable here, as they can present your portfolio in the best light and direct you to lenders with the most pragmatic approach to portfolio assessment.
Since September 2017, the Prudential Regulation Authority (PRA) introduced specific rules for portfolio landlords — defined as anyone with four or more mortgaged buy-to-let properties. If you fall into this category, lenders are required to apply additional scrutiny to your application. A specialist broker can help you navigate these requirements efficiently.
What portfolio landlords need to provide
Full property schedule
- A spreadsheet listing every property you own: address, current value, outstanding mortgage balance, monthly rent, mortgage payment, lender name, and deal expiry date.
Business plan
- Some lenders ask for a brief business plan outlining your investment strategy, how you manage your properties, and your plans for the portfolio over the next 3–5 years.
Cash flow forecast
- Evidence that your portfolio is cash-flow positive or that you have sufficient personal income to cover any shortfalls, including stress-tested scenarios at higher interest rates.
Asset and liability statement
- A summary of your total assets (property values, savings, investments) against total liabilities (mortgages, loans, credit commitments) to demonstrate overall financial health.
Lenders vary widely on portfolio rules
Some lenders cap portfolios at 10 properties, others allow up to 20 or more. Background portfolio requirements also differ — some stress-test your entire portfolio, while others only assess the property you’re applying for. A broker can save you significant time by matching you to the right lender from the start.
Plan your next investment
Related guides
- Stamp Duty Explained
Understand the 5% additional property surcharge and how SDLT bands work for landlords.
- Mortgage Rates Explained
Fixed or tracker — pick the right rate type for your rental cash flow and investment strategy.
- Remortgage Guide
Coming to the end of your BTL deal? Learn when and how to switch for a better rate.
- First-Time Landlord Guide
New to buy-to-let? Our beginner’s guide covers everything from deposits to finding tenants.
- Regulator
- FCA register
- Updated
- 24 February 2026
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