Why BTL Mortgage Tax Planning Matters Now

If you own a buy-to-let property with a mortgage, your tax position has changed significantly over the last decade. The gradual removal of mortgage interest relief for individual landlords, combined with rising interest rates and higher stamp duty surcharges, means the old way of running a portfolio often no longer works.

Many landlords now pay more tax than they did five years ago, even if their rental income hasn't changed. That is not because the rules are unfair. It is because the structure they use to hold their properties is no longer the most efficient one.

As ICAEW qualified accountants, we work with landlords across the UK. From a single flat in Manchester's Northern Quarter to a portfolio of ten houses in Birmingham's Jewellery Quarter. The questions are always the same. Should I incorporate? How do I handle my BTL mortgage interest? What happens when I sell?

This article gives you the answers. It is not generic advice. It is specific, practical, and grounded in the current tax rules for 2025/26.

The Mortgage Interest Restriction: What It Means for You

Since April 2020, individual landlords cannot deduct their mortgage interest costs from rental income before calculating tax. Instead, you get a 20% tax credit on the interest paid. That is the Finance (No.2) Act 2015 change, phased in over four years.

For a basic rate taxpayer, the result is roughly neutral. You lose the deduction but gain a 20% credit. For a higher rate taxpayer (40%) or additional rate taxpayer (45%), the difference is substantial.

Example: A landlord in Leeds with a rental income of £30,000 and mortgage interest of £12,000. Under the old rules, they paid tax on £18,000. Under the current rules, they pay tax on £30,000, then get a 20% credit on the £12,000 interest. A higher rate taxpayer ends up with an extra £2,400 tax bill compared to the old system.

That is the core problem. The restriction does not apply to limited companies. Companies can still deduct mortgage interest as a trading expense. That is the main reason landlords incorporate.

Limited Company vs Personal Ownership: The Numbers

Let us compare two scenarios for a landlord in Bristol with a portfolio of three properties. Total rental income of £60,000 per year. Mortgage interest of £24,000. Other costs (insurance, repairs, letting agent fees) of £8,000.

Personal ownership (higher rate taxpayer):

  • Taxable rental income: £60,000
  • Less other costs: £8,000
  • Net rental income: £52,000
  • Tax at 40%: £20,800
  • Less mortgage interest credit (20% of £24,000): £4,800
  • Total tax: £16,000

Limited company ownership:

  • Rental income: £60,000
  • Less mortgage interest: £24,000
  • Less other costs: £8,000
  • Net profit: £28,000
  • Corporation tax at 19% (small profits rate): £5,320
  • Total tax: £5,320

The difference is £10,680 per year. That is before you take dividends out of the company. Dividends attract further tax at your personal rate (8.75% basic, 33.75% higher, 39.35% additional). But even after dividend tax, the company structure often wins for higher rate taxpayers with significant mortgage interest.

There are costs to running a limited company. Annual accounts, a confirmation statement, corporation tax returns, and payroll if you take a salary. But for portfolios with meaningful mortgage interest, the tax saving usually outweighs the admin cost.

When Incorporation Does Not Make Sense

Incorporation is not always the right answer. If you own one property with a small mortgage or no mortgage, the benefit is smaller. You also face stamp duty land tax when transferring properties into a company. That is a 3% surcharge on top of the normal rates for additional dwellings. On a £200,000 property, that is £6,000 in SDLT alone.

Capital gains tax also applies on the transfer. You are deemed to sell the property at market value when you transfer it to your company. That triggers a CGT charge. For a property that has grown significantly in value, that can be a large bill.

There is a relief called incorporation relief that can defer the gain. It applies if you transfer a business (including a property rental business) as a going concern in exchange for shares. But it is complex and requires the right structure. You need specialist advice before attempting it.

If you are considering incorporation, speak to an accountant first. Do not transfer a property without understanding the SDLT and CGT consequences. Our services page covers how we help landlords with these decisions.

Capital Gains Tax on BTL Property Sales

When you sell a BTL property, you pay capital gains tax on the gain. The rates for residential property are 18% for basic rate taxpayers and 24% for higher rate taxpayers. These rates apply from 30 October 2024 onwards. The old 18% and 24% rates for residential property were introduced in the Autumn Budget 2024.

You must report the gain to HMRC within 60 days of completion. That is done through the 60-day CGT property return. You pay the tax at the same time. If you miss the deadline, HMRC charges interest and penalties.

For a limited company, the gain is taxed as part of the company's profits at corporation tax rates (19% to 25%). That is often lower than the personal CGT rate. But the company cannot use the annual exempt amount (£3,000 for individuals in 2025/26). Companies do not have an annual exempt amount for CGT.

If you hold properties personally and sell, you can use your annual exempt amount each year. That is worth up to £720 in tax saved for a higher rate taxpayer. If you have multiple properties, you can stagger sales across tax years to use multiple annual exempt amounts.

Mortgage Interest and the Company Structure

Within a limited company, mortgage interest is fully deductible against rental income. That is the key advantage. The company pays corporation tax on the net profit after all expenses, including mortgage interest.

There is a catch. If the company makes a loss (because mortgage interest exceeds rental income), the loss can be carried forward against future profits. But you cannot get a refund of corporation tax paid in earlier years. Loss relief is more restrictive for investment companies than for trading companies.

Also, if the company has a large mortgage relative to the property value, HMRC may challenge the interest deduction under the unallowable purpose rules. That is rare for straightforward BTL mortgages, but it can happen if the loan is structured in a way that has no commercial purpose.

Most lenders now offer BTL mortgages to limited companies. The rates are slightly higher than personal BTL mortgages, but the gap has narrowed. Some lenders specialise in company BTL lending. Shop around.

Stamp Duty Land Tax for Company Purchases

When a limited company buys a residential property, it pays the higher rate of SDLT. That is the standard rate plus a 3% surcharge for additional dwellings. There is no exemption for companies buying their first property.

For a property costing £300,000, the SDLT is:

  • 0% on first £250,000: £0
  • 5% on next £50,000: £2,500
  • Plus 3% surcharge on whole £300,000: £9,000
  • Total SDLT: £11,500

That is a significant upfront cost. It is one reason why incorporating an existing portfolio is often better than buying new properties through a company. The SDLT on transfer is a one-off cost. The ongoing tax saving from mortgage interest relief can outweigh it within a few years.

If you are buying a new property, compare the SDLT cost against the annual tax saving. A simple payback calculation tells you whether incorporation is worth it.

Dividend Extraction and Personal Tax Planning

Once your company makes a profit, you need to extract that money personally. The most common method is dividends. Dividends are paid from post-tax profits. The company pays corporation tax first, then distributes the remaining profit as dividends.

Your personal dividend tax rates for 2025/26 are:

  • Dividend allowance: £500 (tax-free)
  • Basic rate: 8.75%
  • Higher rate: 33.75%
  • Additional rate: 39.35%

The dividend allowance has fallen from £2,000 in 2022/23 to £500 now. That means most landlords pay some dividend tax. But the combined tax burden (corporation tax plus dividend tax) is still often lower than personal income tax on rental profits.

You can also take a small salary from the company. A salary of £12,570 (matching the personal allowance) avoids income tax and NIC if the company claims Employment Allowance. That reduces the company's profit and saves corporation tax. It also builds your state pension entitlement.

For a detailed breakdown of director pay strategies, see our director pay and dividends blog.

Making Tax Digital for Landlords

From April 2026, Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) becomes mandatory for landlords with qualifying income over £50,000. From April 2027, it applies to those with income over £30,000. From April 2028, it applies to those with income over £20,000.

If you hold properties personally, you will need to keep digital records and submit quarterly updates to HMRC. That means using compatible software. Xero, FreeAgent, and QuickBooks all support MTD for ITSA. If you use a spreadsheet, you will need bridging software to submit the data.

For company landlords, the company already files corporation tax returns annually. MTD for ITSA does not apply to companies. But if you take dividends personally, your personal tax return will be within MTD for ITSA if your total income (including dividends) exceeds the threshold.

Start preparing now. If your rental income is close to the threshold, consider whether you can reduce it through legitimate expenses or restructuring. Our MTD blog has more detail on the requirements.

Other Tax Reliefs for Landlords

Beyond mortgage interest, there are other reliefs you should know about.

Capital allowances: If you furnish a property, you can claim capital allowances on furniture, fixtures, and fittings. The Annual Investment Allowance (AIA) of £1,000,000 applies to companies. For individual landlords, the replacement of domestic items relief applies instead. That allows you to deduct the cost of replacing furniture, appliances, and kitchenware, but not the initial cost.

Structures and Buildings Allowance: If you build or renovate a property, you can claim 3% per year on the qualifying costs. That applies to commercial properties and some residential properties used for business purposes.

Repairs and maintenance: You can deduct the cost of repairs and maintenance as a revenue expense. Improvements (that add value or extend the property) are capital and cannot be deducted. The line between repair and improvement is often disputed by HMRC. Keep detailed invoices and descriptions of the work done.

Finance costs: Beyond mortgage interest, you can deduct arrangement fees, valuation fees, and broker fees. These are treated as finance costs and subject to the same restriction for individual landlords.

When to Speak to an Accountant

If you are a landlord with a BTL mortgage, you should review your structure at least once a year. The tax rules change. Your portfolio changes. What worked three years ago may not work now.

Specific triggers for a review:

  • You are a higher rate taxpayer and have mortgage interest of more than £5,000 per year.
  • You are considering buying another property.
  • You are thinking of selling a property.
  • Your rental income has crossed the MTD threshold.
  • You have inherited a property and are deciding whether to keep or sell it.

We help landlords across the UK with these decisions. From a single flat in Edinburgh's Leith to a portfolio in Glasgow's Merchant City. Get in touch through our contact page to discuss your situation.

For a deeper look at the fundamentals of property tax, our fundamentals page covers the core concepts every landlord should understand.