Do you pay SDLT when a co-owner is replaced by a spouse on a mortgaged property?

Introduction

A common question in shared ownership arrangements is whether Stamp Duty Land Tax (SDLT) becomes payable when one joint owner comes off the title and another person, such as a spouse, is added instead. This often happens where siblings bought a property together, one wants to cash out, and the remaining owner refinances the property so that a husband or wife can join the legal title and mortgage.

The answer usually turns on one key point: whether the incoming owner takes on responsibility for existing mortgage debt, or gives any other form of chargeable consideration. Even where part of the equity is effectively gifted, SDLT can still arise because assumption of debt counts as consideration for SDLT purposes.

The Question

In the scenario, two relatives originally bought a property together. The property has increased in value, there is still a substantial mortgage outstanding, and one co-owner now wants to leave the arrangement so they can use their share of the equity towards another home.

The remaining co-owner intends to stay in the property and refinance it with their spouse. As part of that refinance, the outgoing co-owner will be removed from the title and mortgage, the spouse will be added, and borrowing will increase so that the outgoing co-owner can receive their share of the equity.

The issue is whether SDLT is payable when the spouse replaces the outgoing co-owner on the title and mortgage deeds.

Nick’s Explanation

Nick’s central point was that the equity element and the mortgage element must be treated separately.

In anonymised form, his reasoning was:

“A gift of equity, by itself, does not usually create SDLT. But if the incoming owner takes on liability for secured mortgage debt, that assumed debt is treated as chargeable consideration.”

He also identified the practical SDLT question as being the amount of mortgage debt effectively taken on by the incoming spouse. On the facts provided, he treated the incoming spouse as assuming responsibility for half of the existing mortgage debt, which produced a chargeable consideration figure of £160,000 where the outstanding mortgage was about £320,000.

That is the right starting point in principle: SDLT on a transfer of equity is not based simply on market value. It is based on chargeable consideration, and that can include debt taken over by the transferee.

However, the exact SDLT amount depends on the rates in force at the effective date of the transaction and whether the higher rates for additional dwellings apply. The higher rates issue is particularly important where the incoming spouse already owns, or is treated as owning, another dwelling interest.

The Law

SDLT is charged under the Finance Act 2003 on land transactions where there is chargeable consideration.

The key rules are:

• SDLT applies to chargeable consideration given for a land transaction: Finance Act 2003, section 43.
• Chargeable consideration includes money or money’s worth: Finance Act 2003, section 43.
• Where property is transferred subject to an existing mortgage, or the transferee assumes liability for debt, that assumed debt can count as chargeable consideration.
• Special rules can apply to transactions involving connected persons, but for SDLT the market value rule does not apply generally to ordinary transfers unless a specific provision requires it.
• Schedule 4ZA to the Finance Act 2003 contains the higher rates for additional dwellings.

HMRC’s SDLT guidance also recognises that in a transfer of equity, SDLT may arise where the incoming owner takes over responsibility for a share of mortgage debt, even if no cash price is paid directly to the outgoing owner.

Analysis

The analysis can be broken into four steps.

First, identify what is actually being transferred. Here, one existing co-owner is leaving and the remaining co-owner’s spouse is joining. So there is a land transaction involving a transfer of an interest in the property.

Second, identify the chargeable consideration. The outgoing co-owner is receiving value, but for SDLT purposes the crucial point is what the incoming spouse gives or assumes. If the spouse becomes jointly liable under the mortgage, that assumption of debt is treated as consideration.

On the figures provided, the existing mortgage before the refinance is about £320,000. If the spouse is effectively taking on half of that liability, the chargeable consideration would usually be around £160,000.

Third, consider whether the additional borrowing used to release equity changes the SDLT calculation. Usually, SDLT is concerned with the consideration given for the acquired interest. In a transfer of equity case, the key figure is often the share of secured debt assumed in connection with the transfer. Care is needed here because the legal structure of the refinance matters. If the transfer and refinance are implemented as one arrangement, and the incoming spouse becomes liable for a larger amount of secured debt linked to the acquisition, HMRC may look at the actual debt assumed under the transaction documents rather than only the old mortgage balance. The paperwork therefore matters.

Fourth, apply the correct SDLT rates. If the chargeable consideration is £160,000, SDLT is calculated on that figure, not on the full market value of the property and not on the outgoing co-owner’s equity share as such.

The higher rates for additional dwellings may apply if, at the end of the day of the transaction, the incoming spouse owns another dwelling and is not replacing their only or main residence within the meaning of Schedule 4ZA. Whether that surcharge applies cannot be answered safely without knowing the wider property position of both spouses.

If the higher rates do apply, they are charged on the whole of the chargeable consideration. If they do not apply, and the chargeable consideration remains below the ordinary SDLT threshold in force at the effective date, there may be little or no SDLT to pay. The rates and thresholds must be checked for the actual completion date.

It is also important not to confuse SDLT with the fact that money is being raised to pay the outgoing co-owner. The release of equity may be commercially important, but SDLT still depends on the legal consideration for the transfer.

Outcome

In principle, SDLT can arise when a spouse replaces an outgoing co-owner on a mortgaged property, even if part of the arrangement is described as a gift of equity.

The likely reason is that the incoming spouse is assuming liability for mortgage debt, and that assumed debt is chargeable consideration.

On the figures given, a reasonable starting point is that the chargeable consideration is the incoming spouse’s share of the relevant mortgage debt, not the full property value. If that figure is about £160,000, SDLT is assessed on that amount, subject to the rates in force and subject to whether the higher rates for additional dwellings apply.

The exact tax cannot be confirmed from the facts alone because the refinance documents and the spouses’ wider property ownership position could change the result.

Practical Steps

Anyone in this position should check the following before completion:

• Who is transferring what share of the property to whom.
• What mortgage debt exists immediately before the transfer.
• What debt the incoming owner will assume under the transfer and refinance documents.
• Whether any cash or other value is also being given.
• Whether the incoming spouse owns, or is treated as owning, any other dwelling at the end of the transaction.
• Whether the transaction replaces the spouse’s only or main residence for Schedule 4ZA purposes.
• What SDLT rates and thresholds apply on the actual effective date.

It is sensible to ask the conveyancer or SDLT adviser to calculate the tax by reference to the transfer deed and mortgage arrangements together, rather than looking only at the equity payment in isolation.

Conclusion

Where one co-owner leaves a mortgaged property and a spouse takes their place, SDLT is often triggered by the spouse taking on mortgage debt. A gift of equity on its own may not be taxable, but assumption of debt usually is. The correct SDLT figure depends on the amount of debt assumed, the completion date rates, and whether the higher rates for additional dwellings apply.

Legal References Used

• Finance Act 2003, section 43
• Finance Act 2003, Schedule 4ZA
• HMRC Stamp Duty Land Tax guidance on chargeable consideration and transfers subject to mortgage debt

This page was last updated on 22 March 2026.

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