Can one joint purchaser amend an SDLT return, or must both jointly authorise it?

Introduction

Readers often search for this issue when HMRC challenges a Stamp Duty Land Tax (SDLT) amendment or refund on the basis that a property was bought jointly, but only one purchaser appears to have authorised the amendment. This can arise in claims involving mixed-use treatment or Multiple Dwellings Relief (MDR), especially where an agent submitted the amendment after completion.

The key question is whether the SDLT legislation requires both joint purchasers to give separate express authority, or whether one joint purchaser or an authorised agent can act for both. The answer matters because HMRC may try to invalidate a repayment claim on what is, in substance, a procedural point.

The Question

A married couple bought a property jointly. After completion, an SDLT amendment was made through an adviser, seeking a repayment based on the way the property should be treated for SDLT purposes. HMRC later argued that the amendment was invalid because both joint purchasers had not expressly authorised it, and that the repayment should therefore be recovered.

The couple wanted to know whether HMRC was right to say that both purchasers had to sign or separately authorise the amendment, and whether that technical argument could defeat the underlying SDLT claim.

Nick’s Explanation

Nick’s central view was that HMRC’s argument on authorisation was weak. In anonymised form, his reasoning was:

“HMRC are arguing that the refund is invalid because both joint purchasers did not provide express authorisation for the amendment. This is essentially a technical point. However, there are grounds to rebut this argument, as there is no clear requirement in the legislation that both parties must sign or authorise an amendment. In practice, one joint purchaser or their agent can often act for both, especially under agency law principles.”

He also pointed out that this issue should be treated separately from the substantive SDLT position. In other words, even if HMRC raises a procedural objection, the stronger issue usually remains whether the underlying claim was correct on the facts.

Where the substantive claim concerns mixed-use treatment or whether part of a building was unsuitable for use as a dwelling, the factual evidence remains critical. 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.

The Law

The starting point is section 103 Finance Act 2003, which deals with joint purchasers. It provides:

“(1) This section applies to a land transaction where there are two or more purchasers who are or will be jointly entitled to the interest acquired.

(2) The general rules are that—
(a) any obligation of the purchaser under this Part in relation to the transaction is an obligation of the purchasers jointly but may be discharged by any of them,
(b) anything required or authorised by this Part to be done in relation to the purchaser must be done by or in relation to all of them, and
(c) any liability of the purchaser under this Part in relation to the transaction … is a joint and several liability of the purchasers.”

This wording matters. Paragraph (a) expressly says that a joint obligation may be discharged by any of the joint purchasers. Paragraph (b) says that things required or authorised to be done in relation to the purchaser must be done by or in relation to all of them. That does not expressly say each purchaser must physically sign every document or give separate written authority in every case.

Schedule 10 Finance Act 2003 is also relevant. Paragraph 6(1) states:

“The purchaser may amend a land transaction return given by him by notice to the Inland Revenue.”

That provision contemplates amendments being made within the SDLT self-assessment framework. In practice, amendments are often made through solicitors or tax agents acting for the purchaser or purchasers.

On the wider approach to SDLT, the Upper Tribunal in HMRC v Ridgway [2024] UKUT 36 (TCC) rejected an overly formalistic approach to SDLT claims. The case is better known for dwelling suitability issues, but it is still relevant as an example of the tribunal focusing on the real legal and factual position rather than letting procedural form eclipse substance.

Where the issue is whether a building was suitable for use as a dwelling, the Court of Appeal in Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799 is now particularly important. It confirms that the threshold for showing a property was not suitable for use as a dwelling is relatively high.

Analysis

The practical analysis usually has four steps.

First, identify what HMRC is actually arguing. If HMRC says the amendment is invalid because both joint purchasers did not expressly authorise it, that is a procedural challenge to the amendment itself. It is not necessarily a finding that the substantive SDLT analysis is wrong.

Second, examine the statutory wording closely. Section 103 Finance Act 2003 does not clearly impose a rule that both joint purchasers must each sign an amendment. The phrase “done by or in relation to all of them” is capable of covering action taken on behalf of both purchasers, particularly where one purchaser instructed the adviser and there is no evidence that the other objected.

Third, consider ordinary agency principles. In tax administration, it is common for one purchaser to deal with the conveyancer or tax adviser on behalf of both buyers. HMRC’s own systems have long operated on the basis that agents can file returns and amendments without collecting separate signatures for every procedural step. That does not prove every filing is valid, but it does show why HMRC may struggle to argue that Parliament intended a rigid two-signature rule unless the legislation says so clearly.

Fourth, keep the substantive SDLT issue separate and properly evidenced. If the claim is based on mixed-use, the evidence must support mixed-use. If it is based on MDR, the facts must support MDR. If it is based on the property being uninhabitable or not suitable for use as a dwelling, the current legal threshold is demanding. Following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799, poor condition alone may not be enough unless the defects are serious enough to take the property outside the statutory concept of a dwelling.

That means a taxpayer should not rely only on the authorisation point. Even if HMRC’s technical objection is weak, the underlying SDLT basis must still stand up.

Outcome

The practical takeaway is that HMRC does not appear to have an obvious statutory basis for saying that every SDLT amendment by joint purchasers is invalid unless both purchasers separately sign or expressly authorise it. There is a credible argument that one joint purchaser, or an authorised agent, can act for both, provided the amendment is made in relation to both purchasers and there is no evidence of lack of authority.

However, success will usually depend on more than that. A taxpayer still needs a strong substantive case for the repayment or relief claimed. If the argument is mixed-use, MDR, or unsuitability for use as a dwelling, the facts must support it.

Practical Steps

If you are in this position, the sensible next steps are:

• Obtain and review the original SDLT return, the amendment, and all correspondence with HMRC.
• Check who instructed the conveyancer or tax adviser and whether there is evidence that the adviser was acting for both purchasers.
• Gather documents showing the other joint purchaser knew of, approved, or at least did not oppose the amendment.
• Separate the procedural issue from the substantive SDLT issue and prepare both arguments clearly.
• If the claim depends on mixed-use, collect plans, title documents, photographs, valuation material, and evidence of non-residential use.
• If the claim depends on habitability or suitability for use as a dwelling, assess the evidence against the now relatively high threshold following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799.
• If a tribunal deadline is close, file the core response in time and state that further evidence will follow if necessary.

Conclusion

HMRC may try to defeat a joint purchasers’ SDLT amendment on the basis that both buyers did not expressly authorise it, but the legislation does not clearly require two separate signatures for every amendment. There is a respectable argument that one joint purchaser or an authorised agent can act for both. Even so, the strongest position will usually combine that procedural rebuttal with solid evidence that the underlying SDLT treatment was correct.

Legal References Used

• Finance Act 2003, section 103
• Finance Act 2003, Schedule 10, paragraph 6(1)
• HMRC v Ridgway [2024] UKUT 36 (TCC)
• 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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