Does SDLT include a co-owner’s share of a mortgage if the loan was only in one buyer’s name?

Introduction

This is a common SDLT question where one co-owner buys out another person’s share in a property, but the mortgage was never actually in both names. The issue is whether the outgoing owner’s “share” of the mortgage should be treated as chargeable consideration for Stamp Duty Land Tax.

Readers usually search for this when a solicitor has included part of an outstanding loan in the SDLT calculation, even though only one person was personally liable to the bank. The answer depends on whether the outgoing owner was truly being released from a real debt or legal liability, or whether there was only a charge over the property without personal liability.

The Question

A taxpayer bought out a minority co-owner’s share in a commercial property. The property was subject to a mortgage, but the borrowing was in the taxpayer’s sole name. SDLT was calculated on:

• the cash paid for the outgoing co-owner’s equity, and
• an additional amount said to represent that co-owner’s proportion of the outstanding mortgage.

The taxpayer questioned whether that extra mortgage element should have been included at all, because the outgoing co-owner had never been a borrower under the loan. However, the bank did hold security over that co-owner’s interest in the property, and the co-owner would be released from that security when the transfer completed.

The practical question was whether the release from that security amounted to chargeable consideration for SDLT.

Nick’s Explanation

Nick’s core view was that there may be a strong argument that the mortgage-related amount should not be treated as chargeable consideration if the outgoing co-owner was never personally liable for the debt.

In anonymised form, his reasoning was:

“If the person was not personally liable for the mortgage, and their only connection was a security charge over their share of the property, there is a good argument that the amount should not be included as chargeable consideration.”

He also identified the key legal question correctly: did the security have real legal weight in the sense of creating an enforceable financial liability for that person, or was it only security over property without personal repayment liability?

He explained the point in practical terms:

• If the person would actually have been liable to repay the relevant debt on default, HMRC would be more likely to say that the buyer assumed or released debt, which can count as consideration.
• If the person was not directly liable on the loan, and the bank’s rights were limited to enforcing its security against the property interest, that is a different position.

The bank correspondence in this scenario was important because it said, in substance, that only the borrower was liable for the outstanding loan and that the other co-owner was not directly liable on the loan. That supports the argument that there was no personal debt of the outgoing co-owner for the buyer to assume or discharge.

Nick therefore asked to see the original security document, because the exact wording matters. A security document can sometimes do more than simply charge property. In some cases it may contain wider obligations, guarantees, indemnities, or capped liabilities which could affect the SDLT analysis.

The Law

SDLT is charged on the chargeable consideration for a land transaction under the Finance Act 2003.

The starting point is that chargeable consideration includes money or money’s worth given for the land. It can include not only cash paid to the seller, but also debt taken on, debt released, or other liabilities assumed as part of the transaction.

The relevant rule is found in Schedule 4 to the Finance Act 2003. Paragraph 8 provides:

“Debt as consideration

8(1) Where the chargeable consideration for a land transaction consists in whole or in part of—

(a) the satisfaction or release of a debt due to the purchaser or owed by the vendor, or

(b) the assumption of existing debt by the purchaser,

the amount of the debt satisfied, released or assumed shall be taken to be the whole or part, as the case may be, of the chargeable consideration for the transaction.”

In plain English, if the buyer takes over a debt that the seller owed, or if the transaction releases the seller from a debt, that debt can count as SDLT consideration.

But the rule only works where there is in fact a debt owed by the seller or an existing debt assumed by the buyer. A charge over land is not automatically the same thing as personal liability for the underlying borrowing.

That distinction matters. A person may own property subject to a legal charge or restriction, but still not be personally liable to repay the bank loan unless they have also signed as borrower, guarantor, indemnifier, or otherwise undertaken enforceable payment obligations.

Analysis

The SDLT position can be analysed in stages.

First, identify the cash consideration. If the buyer paid a sum for the outgoing co-owner’s equity, that cash is plainly chargeable consideration.

Second, ask whether there was any additional debt-related consideration. This depends on whether the outgoing co-owner was under a real debt or liability that the buyer’s acquisition relieved them from.

Third, separate personal debt from proprietary security. These are not the same thing:

• Personal debt means the bank can sue the person directly for repayment.
• Security means the bank can enforce against charged property or a charged interest, but not necessarily sue that person as borrower.

Fourth, apply that distinction to the facts. Here, the available evidence suggested:

• the mortgage loan was in the buyer’s sole name;
• the outgoing co-owner was not directly liable on the loan;
• the bank had recourse to security affecting that co-owner’s interest in the property.

On those facts alone, the stronger argument is that the outgoing co-owner did not owe a share of the mortgage debt personally. If that is right, the buyer did not assume that person’s debt, and the transaction did not release that person from a personal debt within paragraph 8 of Schedule 4 to the Finance Act 2003.

Fifth, review the security document carefully. This is the critical evidential step. The quoted wording referred to a security granted for the obligations of the borrower and a monetary cap on the amount recoverable by the bank under that security. That wording may indicate that the co-owner granted security for another person’s obligations, but it does not automatically prove personal liability as borrower.

However, the drafting must be checked in full. Some security documents create additional obligations. For example, a document may include:

• a guarantee;
• an indemnity;
• a covenant to pay on demand;
• joint and several liability wording; or
• other personal undertakings beyond the charged asset itself.

If any of those features are present, HMRC may argue that the outgoing co-owner did have a real financial liability, and that release from that liability formed part of the consideration.

If they are absent, and the document only created security over the co-owner’s interest in the property, the argument for excluding the mortgage-related amount becomes much stronger.

Sixth, consider the amendment window. In the underlying correspondence, the transaction had taken place within the previous 12 months. That is important because SDLT return amendments are generally easier to deal with within the statutory amendment period. Timing can therefore be crucial if the original return overstated the chargeable consideration.

Finally, this is not an “uninhabitable” or “unsuitable for use” case, but readers often encounter both issues together in SDLT disputes. In any genuinely uninhabitable case, it is important to note that the condition thresholds are now relatively high following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.

Outcome

If the outgoing co-owner was not personally liable for the mortgage, and was only subject to a security over their property interest, there is a credible argument that their supposed share of the outstanding mortgage should not have been included as SDLT consideration.

In that situation, SDLT should usually be calculated only on the actual consideration given, such as the cash paid for the equity acquired, unless the documents show some further enforceable liability.

But the final answer depends on the exact terms of the security document. The paperwork must show whether the outgoing co-owner merely charged their interest as security, or whether they also undertook personal liability in some legally meaningful way.

Practical Steps

If you are checking whether SDLT was overpaid in a similar buyout, work through the following:

• Obtain the SDLT return and completion statement to see exactly how the consideration was calculated.
• Get the mortgage offer and facility letter to confirm who the actual borrower was.
• Obtain the legal charge, deed of security, guarantee, indemnity, or any side letter signed by the outgoing owner.
• Check whether the bank could pursue that person personally for repayment, or only enforce against the property interest.
• Look for wording such as “guarantee”, “indemnity”, “covenant to pay”, “joint and several”, or “personally liable”.
• Check the transaction date to see whether the SDLT return can still be amended or whether a repayment claim route is needed.
• If the wording is unclear, have the security document reviewed by a lawyer or SDLT specialist familiar with debt-as-consideration issues.

The key documentary question is simple: was the outgoing owner released from an actual debt, or only from a charge over the property?

Conclusion

Where one co-owner buys out another, a mortgage element is not automatically part of SDLT consideration just because the property was charged. If the outgoing owner was never personally liable for the borrowing, there may be a strong argument that no debt was assumed or released for SDLT purposes. The decisive point is the legal effect of the security document.

Legal References Used

• Finance Act 2003
• Finance Act 2003, Schedule 4, paragraph 8
• 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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