Buying a House with an Annexe: SDLT Guide Post-MDR Abolition
Multiple Dwellings Relief was abolished on 1 June 2024. SDLT on a property with an annexe now turns on a single pivotal question: is the annexe a legally separate dwelling, or part of the main house?
Last verified: April 2026
Key Takeaways
- •Multiple Dwellings Relief (MDR) was abolished effective 1 June 2024 — it is no longer available for most purchases.
- •If the annexe is a separate dwelling, each part of the property is taxed on its apportioned value — often a lower total.
- •If the annexe is integrated, the full combined price is taxed as one residential property.
- •On a £380,000 purchase (house + separate annexe), the SDLT difference can be £4,000 depending on classification.
- •An annexe used as an office but physically self-contained can still be classified as a separate dwelling by HMRC.
In this article
MDR Abolished: What Changed
Multiple Dwellings Relief (MDR) was a valuable SDLT relief that allowed buyers purchasing two or more dwellings in a single transaction to calculate their SDLT by reference to the mean (average) consideration per dwelling. For a house with a self-contained annexe, this often produced a significantly lower SDLT bill than taxing the combined price.
Finance Act 2024 abolished MDR with effect from 1 June 2024. The government's stated rationale was that the relief was being used beyond its original policy intention — particularly by buyers of high-value properties who apportioned prices to minimise tax, sometimes on the basis of marginal or disputed self-contained areas.
Post-abolition, the SDLT treatment of a house with an annexe is determined entirely by whether each part constitutes a separate dwelling for SDLT purposes — a factual question with significant financial consequences.
MDR cannot be claimed for 2024/2025/2026 purchases unless your contract was exchanged on or before 6 March 2024. Any buyer who has been advised they can still use MDR on a recent purchase should seek an immediate second opinion.
Separate Dwelling vs Integrated Annexe
The term "dwelling" is defined in s.116 Finance Act 2003 as a building (or part) used or suitable for use as a single dwelling. The key phrase is "suitable for use" — current use is not determinative. An annexe that is physically capable of independent occupation will generally be treated as a separate dwelling even if currently used as a garage, office, or guest room.
HMRC applies a multi-factor test to assess whether an annexe is a separate dwelling:
Factors pointing to SEPARATE dwelling
- •Own entrance (not through main house)
- •Self-contained kitchen facilities
- •Own bathroom and/or WC
- •Separate utility meters
- •Could be let independently
- •Separate postal address
Factors pointing to INTEGRATED annexe
- •Access only through main house
- •No kitchen or cooking facilities
- •No independent bathroom
- •Shared utilities with main house
- •Requires main house for essential functions
- •Below minimum habitable size
No single factor is conclusive. HMRC assesses the totality of the evidence. A planning permission classifying the annexe as ancillary accommodation is one indicator, but it is not binding on HMRC's SDLT assessment. Similarly, council tax banding can be relevant but is not determinative.
HMRC guidance: See SDLTM00370 for HMRC's interpretation of "dwelling" in the context of SDLT. Where there is genuine uncertainty about classification, professional advice should be obtained before completion.
Calculation Examples
A buyer purchases a house for £380,000 total, comprising a main house valued at £300,000 and an annexe valued at £80,000.
Scenario A: Annexe is a Separate Dwelling
Each part is taxed on its apportioned consideration individually.
Main house — £300,000
Annexe — £80,000
Scenario B: Annexe is Integrated (Single Property)
Full £380,000 taxed as one residential property.
Correct SDLT classification can save £4,000 on this example. For higher value properties the difference is larger.
If You Already Own Another Property
If you already own another residential property at the time of purchase (triggering the 5% additional dwelling surcharge), the higher rates apply to every dwelling in the transaction — whether the annexe is classified as separate or integrated.
| Scenario | Standard Buyer | Additional Property Buyer |
|---|---|---|
| Separate dwellings (£300k + £80k) | £5,000 | £24,000 |
| Integrated single property (£380k) | £9,000 | £28,000 |
Surcharge on both dwellings: When the annexe is a separate dwelling and the buyer already owns another property, the 5% surcharge applies to both the main house and the annexe. Each is taxed at higher rates on its apportioned value. There is no exemption for the annexe portion.
Transitional MDR Rules
MDR was abolished for transactions with an effective date (completion) on or after 1 June 2024, with an important transitional provision: contracts exchanged on or before 6 March 2024 can still use MDR, provided the contract has not been varied or assigned since that date.
This means a relatively small number of transactions that were exchanged before Budget day 2024 and completed after June 2024 could still benefit from MDR. Any variation to such a contract — for example, a price reduction, a change of parties, or an extension of the completion date by agreement — would cause the transitional protection to fall away.
For any transaction exchanged after 6 March 2024, MDR is simply not available. There is no transitional protection, and the SDLT calculation must follow the post-abolition rules described in this guide.
MDR Availability Flowchart
Frequently Asked Questions
How does HMRC decide if an annexe is a separate dwelling?
HMRC examines whether it has independent access, separate utilities, a kitchen and bathroom, and whether someone could genuinely live there independently. No single factor is decisive — the assessment is based on the overall facts and physical characteristics of the annexe. HMRC's guidance at SDLTM00370 outlines the approach.
Can I claim MDR in 2026?
Only if your contract was exchanged on or before 6 March 2024 without any variation or assignment of rights since that date. All other purchases are subject to the post-abolition rules where MDR is simply not available. If you exchanged before that date, take specialist SDLT advice to confirm the position before filing your return.
We're using the annexe as an office, not a home. Does it still count?
Classification depends on whether it has the physical characteristics of a dwelling, not its current use. An annexe that is physically self-contained — with independent access, kitchen, and bathroom — may still be treated as a separate dwelling even if it is used as an office. HMRC will look at what the building is capable of being used for, not what it is currently used for.
What if we're buying with a mortgage on the whole property including annexe?
The mortgage structure does not affect SDLT classification. SDLT is based on the legal and physical characteristics of the property, not how it is financed. A single mortgage covering both the main house and annexe does not make the annexe integrated — and separate mortgages do not make the annexe a separate dwelling. The physical facts of the property are what matter.
Emma Richardson, MRICS
Chartered Surveyor & Property Tax Specialist
Emma Richardson is a RICS-qualified Chartered Surveyor with over 12 years of experience in UK property taxation. She founded Calculate My Stamp Duty UK to help buyers understand the complex world of property transaction taxes.
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