Converting a Property to an HMO: The Tax Implications You Must Plan For

Converting a property to a house in multiple occupation changes its tax position across income tax, stamp duty land tax and capital gains tax, and the HMO tax rules UK landlords must follow reward careful planning before the works begin. Rental profits from a HMO are usually taxed as property income like any let, but the higher running costs, mandatory licensing and additional stamp duty make the numbers materially different from a single-let buy-to-let. Blue Tick Accountants, a Guildford-based UK tax advisory and accountancy practice, helps landlords structure HMO conversions so the tax cost is understood before completion, not discovered after it. This article explains how HMO income is taxed, which expenses you can claim, and the stamp duty and capital gains position to model before converting.

Key Takeaways

• HMO rental profits are generally taxed as property income for income tax, at the landlord's marginal rate of 20%, 40% or 45% in 2026/27.
• The Section 24 finance cost restriction limits mortgage interest relief for individual landlords to a basic-rate 20% tax reduction, which applies to HMOs the same way it applies to standard buy-to-lets.
• HMO licensing fees and safety certificate costs are generally deductible as revenue expenses against rental income.
• Buying an additional residential property such as a HMO attracts standard SDLT plus a 5% higher-rate surcharge on the whole purchase price in 2026/27.
• Capital gains tax on the sale of a residential HMO is charged at 18% for basic-rate taxpayers and 24% for higher-rate taxpayers, after the £3,000 annual exempt amount.
• Landlords with qualifying property income above £50,000 must keep digital records and file quarterly updates under Making Tax Digital for Income Tax from 6 April 2026.

How is HMO rental income taxed in 2026/27?

HMO rental income is taxed as property income at the landlord's marginal rate of 20%, 40% or 45%, calculated on the profit after allowable expenses. In most cases letting a HMO does not amount to a trade, so the income sits within the property business rules rather than being taxed as self-employment. This matters because the Section 24 finance costs restriction applies: individual landlords cannot deduct mortgage interest as an expense and instead receive only a basic-rate 20% tax reduction on their finance costs, which is significant where mortgage interest on a converted property is substantial.

For a fuller treatment of house in multiple occupation tax, see our guide to HMO tax rules.

What expenses can an HMO landlord claim?

An HMO landlord can deduct the day-to-day running costs of the property from rental income, and HMOs generate more of these costs than a single let. Allowable revenue expenses include letting agent fees, buildings and contents insurance, repairs, and the utilities and council tax a landlord typically pays where bills are included in the rent. Mandatory HMO licence fees, gas safety certificates, electrical inspections and fire safety compliance costs are also generally deductible.

Capital costs are treated differently. The conversion works themselves, such as adding bedrooms, en-suites or a new kitchen, are usually capital and not deductible against rental income, although they reduce a future capital gains tax bill. Replacing worn items on a like-for-like basis is normally an allowable repair. The line between a repair and an improvement is a common area where HMO landlord HMRC enquiries arise, so keeping clear records of every conversion cost is essential.

How much SDLT and CGT apply to an HMO?

Buying an HMO usually attracts stamp duty land tax at the standard residential rates plus a 5% higher-rate surcharge, and selling one triggers capital gains tax at the 18% and 24% rates. An HMO is treated as residential property for SDLT, so the additional dwellings surcharge applies where it is a second or subsequent property. Multiple dwellings relief was abolished from 1 June 2024.

Consider a landlord buying a property for £300,000 to convert into an HMO as an additional property. Standard SDLT is £5,000 (nil on the first £125,000, 2% on the next £125,000 and 5% on the final £50,000), and the 5% surcharge adds £15,000 on the full price, giving a total SDLT bill of £20,000. On a later sale, any gain is charged after the £3,000 annual exempt amount at 18% for a basic-rate taxpayer or 24% for a higher-rate taxpayer, with qualifying conversion costs added to the base cost to reduce the taxable gain.

Frequently Asked Questions

Is HMO income taxed differently from normal rental income?

HMO income is generally taxed the same way as normal rental income, as property income at the landlord's marginal rate of 20%, 40% or 45% in 2026/27. The Section 24 finance cost restriction and the standard property expense rules both apply. The main differences are practical: higher running costs, licensing obligations and different stamp duty on purchase.

Can I claim HMO licensing fees against tax?

Yes. HMO licensing fees are generally deductible as a revenue expense against rental income, along with gas safety certificates, electrical inspections and fire safety compliance. These are recurring costs of running the property rather than capital improvements, so they reduce your taxable rental profit in the year they are incurred.

Do I pay extra stamp duty when buying an HMO?

Usually yes. An HMO is residential property for stamp duty land tax, so buying it as an additional property attracts standard residential SDLT plus a 5% higher-rate surcharge on the whole price in 2026/27. On a £300,000 purchase this means a total SDLT bill of around £20,000.

Are conversion costs tax deductible?

Conversion costs are usually capital rather than revenue, so creating extra bedrooms, en-suites or a new kitchen cannot normally be deducted against rental income. Instead these capital costs are added to the property's base cost and reduce the capital gains tax due when you sell. Genuine repairs, such as like-for-like replacements, remain deductible against rental income.

What CGT will I pay when I sell an HMO?

Capital gains tax on a residential HMO is charged at 18% for basic-rate taxpayers and 24% for higher-rate taxpayers in 2026/27, after deducting the £3,000 annual exempt amount. Your taxable gain is the sale price less the original purchase price, buying and selling costs, and qualifying capital improvements such as conversion works.

How Blue Tick Can Help

Blue Tick Accountants advises landlords converting property to HMOs, modelling the income tax, stamp duty and capital gains position before the works start so there are no surprises at completion or sale, and helping HMO landlords capture every allowable expense and record conversion costs for future capital gains relief. Head to our website and book a meeting now.

Conclusion

Converting a property to a HMO can lift rental yields, but it also raises the tax stakes across income tax, stamp duty and capital gains. Model the extra stamp duty, the Section 24 restriction on your mortgage interest, and the treatment of conversion costs before committing, and keep meticulous records of every capital and revenue cost. Planning the tax position first is the difference between a profitable HMO and an expensive surprise.

About the Author

This guide was written by Leon, founder of Blue Tick Accountants, a Guildford-based UK tax advisory and accountancy practice that helps landlords, the self-employed and limited company owners across the UK. It was last reviewed for the 2026/27 tax year.

This article is intended for general informational purposes only and does not constitute tax, legal, or financial advice. Tax rules are subject to change and their application will depend on your individual circumstances. You should always seek advice from a qualified professional before taking action. Blue Tick Accountants accepts no liability for decisions made on the basis of this content.

Related reading: HMO vs Standard Buy-to-Let: Which Is More Tax Efficient?.

Related reading: CGT on HMO Disposals: How Is It Different from Standard Buy-to-Let?.