Do you pay extra SDLT if a buy-to-let property includes an annex or cottage?

Introduction

Buyers often ask whether Stamp Duty Land Tax (SDLT) changes if a property includes a separate annex, cottage or other additional accommodation within the same title. A common concern is whether the smaller unit creates an extra SDLT charge, or whether its lower value can reduce the overall bill.

This question has become more important since the abolition of Multiple Dwellings Relief (MDR) for most transactions completing on or after 1 June 2024. Where a purchase includes more than one dwelling, the old rules could sometimes reduce SDLT. In many current transactions, that is no longer the case.

The Question

A married couple already own a home and are buying a residential investment property for £1 million. The property includes a main house and a smaller annex or cottage within the grounds. Everything is being sold under a single registered title. They understand that the higher rates for additional dwellings will apply because this is an additional residential purchase. They want to know whether:

• the annex creates any extra SDLT charge, and
• the annex’s lower value, possibly below £125,000, reduces the SDLT payable.

Nick’s Explanation

Nick’s answer was that the purchase price is taxed as a single land transaction unless a specific relief applies. In anonymised form, his reasoning was:

“Because the buyers already own another property, the higher additional dwelling rates apply. Although there is a smaller annex or cottage within the same title, Multiple Dwellings Relief is no longer available for a transaction taking place now, unless it falls within the limited transitional rules. SDLT is therefore charged on the full £1 million consideration. The fact that the smaller dwelling may be worth less than £125,000 does not reduce the SDLT.”

He also made the practical point that there is no separate SDLT penalty just because there is an annex. The issue is simply that, without a relief such as MDR, there is no mechanism to split the price and tax part of it separately.

The Law

SDLT is charged under Finance Act 2003 on a land transaction by reference to the chargeable consideration given for that transaction. In straightforward terms, that usually means the total price paid for the property interest being acquired.

Where a buyer acquires a residential property and already owns another dwelling, the higher rates for additional dwellings may apply, subject to the detailed replacement of main residence rules and other exceptions.

Before its abolition, Multiple Dwellings Relief could apply where two or more dwellings were acquired in a single transaction or linked transactions. Broadly, the tax was calculated by reference to the average price per dwelling, subject to a minimum rate. That relief was abolished for transactions with an effective date on or after 1 June 2024, except where transitional protection applies, broadly where contracts were exchanged on or before 6 March 2024 and were not subsequently varied or assigned.

The key point is that SDLT is not normally reduced just because part of the property could be viewed as a smaller or lower-value dwelling. A statutory relief is needed before the transaction can be taxed on a different basis.

If a buyer is considering whether an annex is a separate dwelling for SDLT purposes, that question can still matter in some contexts. However, in an uninhabitable or not suitable for use case, the condition thresholds are now relatively high following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

Analysis

The SDLT position can be worked through in stages.

1. Identify the transaction.

   Here, the buyers are purchasing one property interest under a single title for a total of £1 million. That is the starting point for SDLT.

2. Decide whether the higher rates apply.

   Because the buyers already own another dwelling and this purchase is an additional residential property, the higher rates for additional dwellings are likely to apply.

3. Consider whether the annex changes the SDLT structure.

   The presence of an annex or cottage does not automatically create a second SDLT charge. Nor does it automatically allow part of the price to be taxed separately.

4. Consider whether any relief applies.

   Historically, MDR might have helped if both the main house and the annex qualified as separate dwellings. But for most current transactions, MDR has been abolished. If the transaction does not fall within the transitional rules, that route is closed.

5. Check whether the annex’s lower value matters.

   It does not, by itself. SDLT is charged on the whole of the chargeable consideration for the land transaction. There is no general rule allowing the buyer to carve out the annex and say that its value falls below a threshold.

So, if the transaction completes now and does not qualify for transitional MDR treatment, the whole £1 million is charged at the residential rates applicable to an additional dwelling purchase.

Outcome

The practical answer is:

• there is no separate extra SDLT charge just because the property includes an annex or cottage;
• however, there is also no SDLT reduction simply because that annex may have a low standalone value;
• if MDR is not available, SDLT is calculated on the full purchase price of £1 million; and
• if the buyers already own another dwelling, the higher rates for additional dwellings are likely to apply to that full amount.

Practical Steps

If you are assessing a similar purchase, it helps to check the following:

• whether the property is being bought under one title or multiple titles;
• whether there are genuinely two or more dwellings within the property;
• whether the transaction could fall within the transitional rules preserving MDR, for example because contracts were exchanged on or before 6 March 2024 and not varied afterwards;
• whether the higher rates for additional dwellings apply based on your existing property ownership and intended use;
• whether any unusual features could affect the analysis, such as mixed-use treatment or replacement of a main residence; and
• whether the annex is being described as uninhabitable, bearing in mind that the threshold for not suitable for use arguments is now relatively high after Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

In practice, the SDLT calculation usually turns on the legal structure of the transaction and the availability of a statutory relief, not simply on the separate value of the annex.

Conclusion

Where a buy-to-let purchase includes a main house and an annex within the same title, SDLT is generally charged on the full purchase price. Since MDR was abolished for most transactions completing on or after 1 June 2024, the annex will not usually reduce the SDLT bill, even if it might be worth less than £125,000 on its own.

Legal References Used

• Finance Act 2003
• Finance Act 2003, SDLT provisions on chargeable consideration
• Finance Act 2003, higher rates for additional dwellings
• Legislation abolishing Multiple Dwellings Relief for transactions with an effective date on or after 1 June 2024, subject to transitional rules
• Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799

This page was last updated on 22 March 2026.

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