Do you pay SDLT when transferring a share of a mortgaged family home to a sibling?

Introduction

People often assume that no Stamp Duty Land Tax (SDLT) is due if no cash changes hands on a family transfer. That is not always right. Where a person takes over responsibility for a mortgage, HMRC can treat that assumed debt as chargeable consideration for SDLT purposes.

This issue commonly arises when one co-owner wants to come off the mortgage and title, and another family member is added so the property can stay in the family. The key questions are usually:

• does the transfer count as a land transaction,
• is the mortgage debt treated as consideration,
• is any SDLT actually payable, and
• do the higher rates for additional dwellings apply?

The Question

A co-owner of a family home wanted to come off both the mortgage and the legal title so they could later buy a home of their own. The plan was for a sibling to be added to the mortgage and title, with the outgoing co-owner then transferring their share.

No money would be paid for the transfer itself, but the property was still subject to a mortgage of about £219,131. On the assumed facts, the outgoing owner’s share of that mortgage was about £109,566.

The main concern was whether the transfer to the sibling would trigger SDLT, especially where the sibling already owned another residential property.

Nick’s Explanation

Nick’s core point was that SDLT is not limited to cash payments. If the incoming owner takes over liability for mortgage debt, that debt can count as consideration.

In anonymised form, his reasoning was:

• the transfer of the outgoing owner’s share is a land transaction,
• the incoming sibling’s assumption of mortgage liability is chargeable consideration under Schedule 4, paragraph 8 Finance Act 2003,
• if only half the mortgage is effectively being taken on at that stage, the chargeable consideration is about £109,566,
• if the purchaser owns no other dwelling, that figure may fall below the ordinary residential nil-rate threshold, so no SDLT may be payable even though the transaction is still chargeable,
• if the purchaser already owns another dwelling and no exception applies, the higher rates under Schedule 4ZA can apply.

Nick also explained that where the consideration exceeds £40,000, an SDLT return may still be needed even if the tax due is nil.

The Law

The main statutory provisions are in the Finance Act 2003.

• Section 43(1) provides that a “land transaction” means an acquisition of a chargeable interest.

• Section 48(1) defines a chargeable interest as an estate, interest, right or power over land in England or Northern Ireland, other than an exempt interest.

• Section 49 says a land transaction is chargeable unless it is exempt from charge.

• Schedule 4, paragraph 8 is critical. Where the purchaser assumes liability for a debt secured on the property, that debt is treated as chargeable consideration.

• Section 77A is relevant to the notification threshold. Transactions below £40,000 are generally outside the SDLT notification requirement, but above that level a return may be required.

• Section 85 provides that the purchaser is liable for any SDLT due.

• Schedule 4ZA imposes the higher rates for additional dwellings where the purchaser acquires a major interest in a dwelling and, at the effective date, owns another dwelling, unless a relieving exception applies.

For the replacement of main residence exception, Schedule 4ZA paragraph 3 can disapply the higher rates in some cases. But that depends on the facts, including whether the purchaser is replacing their only or main residence.

Analysis

Here is how the rules apply step by step.

1. The transfer of the outgoing co-owner’s share is a land transaction

Removing one co-owner from the title and transferring that share to a sibling is an acquisition of a chargeable interest in land. That brings the transaction within sections 43 and 48 Finance Act 2003.

2. No cash does not mean no consideration

This is the point many people miss. If the incoming sibling takes over responsibility for mortgage debt, HMRC treats that assumed debt as consideration under Schedule 4, paragraph 8.

So even if the transfer is described as a gift, the mortgage element can still create SDLT consideration.

3. The amount of chargeable consideration is usually the debt taken on

On these facts, the total mortgage was about £219,131. If the transfer at that stage was only of the outgoing owner’s half share, the relevant consideration was approximately £109,566.

If instead the sibling were treated as taking over the whole mortgage liability in connection with the acquisition, the amount could be higher. The exact figure depends on the legal structure of the transfer and lender arrangements.

4. If the purchaser owns no other dwelling, no SDLT may be payable

Using the figures given, £109,566 is above £40,000, so the transaction is not ignored for SDLT purposes. However, if standard residential rates apply and the chargeable consideration is below the nil-rate threshold in force for the transaction, the SDLT due may still be nil.

That is why a transfer can be both:

• chargeable for SDLT purposes, and
• produce no SDLT liability in money terms.

5. If the purchaser already owns another dwelling, the higher rates may apply

Where the sibling already owns another residential property at the effective date, Schedule 4ZA must be considered. On the facts provided, Nick’s explanation was that the replacement of main residence exception would not apply because the family home would not be the sibling’s replacement only or main residence.

In that situation, the higher rates for additional dwellings apply to the chargeable consideration.

6. The practical SDLT result on the figures provided

Using the figures discussed in the correspondence, and taking the chargeable consideration as £109,566, Nick calculated the SDLT on the basis that the sibling already owned another property. On that basis, SDLT would be payable at the higher residential rates applicable to the transaction.

The correspondence gave an estimated SDLT figure of about £5,478 on those facts. The exact amount should always be checked against the rates in force on the effective date and the precise structure of the transfer.

7. Being an existing co-owner does not automatically prevent SDLT

The fact that the sibling may already be a co-owner or is being added before the outgoing owner is removed does not, by itself, stop SDLT from arising. SDLT looks at the acquisition of chargeable interests and the consideration given, including assumed debt.

So the key issue remains whether, as part of the transaction, the sibling acquires an additional interest and assumes mortgage liability.

8. The outgoing owner’s later purchase is a separate SDLT question

The outgoing owner also asked whether keeping an interest in one property when buying their own home would reduce SDLT. In general, keeping an existing residential interest when buying another dwelling can create higher-rates exposure on the later purchase, unless the replacement of main residence rules apply.

That later purchase is a separate transaction and needs its own analysis based on:

• what interests are still owned at completion,
• whether any previous main residence has been disposed of, and
• whether the replacement of main residence exception can apply.

Outcome

The practical conclusion is:

• Transferring a share of a mortgaged property to a sibling can trigger SDLT even if no money is paid.
• The reason is that the incoming sibling’s assumption of mortgage debt is treated as chargeable consideration.
• If the chargeable consideration is about £109,566 and the sibling owns no other dwelling, SDLT may be nil at standard rates, though an SDLT return may still be required.
• If the sibling already owns another dwelling and no exception applies, the higher rates under Schedule 4ZA can apply and SDLT is likely to be payable.

Practical Steps

If you are considering a similar transfer, it is sensible to work through the following points before documents are signed:

1. Confirm exactly who owns the property now and in what shares.

2. Confirm the current mortgage balance and how much debt the incoming owner will legally assume.

3. Check whether the incoming owner owns any other dwelling at the effective date.

4. Consider whether the replacement of main residence exception in Schedule 4ZA paragraph 3 could apply on the actual facts.

5. Ask the conveyancer to calculate SDLT by reference to the assumed debt, not just any cash paid.

6. Check whether an SDLT return must be filed even if the tax due is zero.

7. If the outgoing owner plans to buy another property, review that later purchase separately to see whether keeping or disposing of the existing interest affects higher-rate SDLT.

If the issue in any case is whether a dwelling was uninhabitable or not suitable for use, readers should note that the condition thresholds are now relatively high following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

Conclusion

A family transfer is not automatically free of SDLT. If a sibling takes over mortgage debt, that debt is usually treated as consideration. Whether any SDLT is actually payable depends mainly on the amount of debt assumed, the rates in force, and whether the purchaser already owns another dwelling so that Schedule 4ZA applies.

Legal References Used

• Finance Act 2003, section 43(1)
• Finance Act 2003, section 48(1)
• Finance Act 2003, section 49
• Finance Act 2003, section 77A
• Finance Act 2003, section 85
• Finance Act 2003, Schedule 4, paragraph 8
• Finance Act 2003, Schedule 4ZA, paragraph 1
• Finance Act 2003, Schedule 4ZA, paragraph 3
• 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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