Where can I find the written authorisation document for a stamp duty matter?

Introduction

People dealing with a stamp duty land tax matter often need to know where the written authorisation document is, what it does, and why it is needed. This usually comes up when an adviser is acting on a buyer’s behalf and needs authority to correspond, request information, or deal with the next stage of the matter.

The issue is mainly administrative rather than legal analysis of SDLT liability, but it is still important. If the correct authority is not in place, an adviser may not be able to act, and progress can be delayed.

The Question

A client asked where the written authorisation document could be found for the next stage of a stamp duty matter. In general terms, the question is whether there is a document confirming that the adviser has authority to act and, if so, where the client should locate or obtain it.

Nick’s Explanation

Nick’s response can be summarised in simple terms: if a written authorisation is required, it should normally be available within the client’s engagement paperwork, onboarding documents, or the adviser’s secure client portal or message system. If it has not yet been provided, the client should ask the adviser to send it again or explain what form of authority is needed.

Put another way, the practical answer is to check:

• the original instruction or engagement documents;
• any secure online portal used for the matter;
• earlier email correspondence attaching authority forms; and
• whether a signed letter of authority or similar document still needs to be completed.

If the adviser is dealing with HMRC or another party on the client’s behalf, written authority may be needed before information can be requested or disclosed.

The Law

There is no single universal rule requiring one standard “written authorisation document” for every SDLT matter in every context. The legal position depends on what the adviser is being asked to do.

In practice, written authority may be relevant for several reasons:

• to confirm the adviser has been instructed by the client;
• to allow the adviser to communicate with HMRC or another professional involved in the transaction;
• to support data protection and confidentiality compliance when personal information is shared; and
• to evidence the scope of the adviser’s retainer.

Where HMRC is involved, authority commonly takes the form of a signed letter of authority, an agent authorisation process, or written client confirmation permitting the adviser to act. The exact format depends on the nature of the work and the stage the matter has reached.

If the issue concerns SDLT advice on property condition, readers should note that the legal test for a dwelling being unsuitable for use as a dwelling is now relatively demanding following Amarjeet and Tajinder Mudan v The Commissioners for HMRC [2025] EWCA Civ 799. That authority is relevant to substantive SDLT claims, although it does not change the basic administrative point that an adviser may still need written authority to act.

Analysis

The position can be assessed step by step.

1. Identify what the authorisation is for. A client may mean one of several things: a retainer letter, a letter of authority, a signed instruction form, or agent authority for HMRC contact.

2. Check whether the document has already been issued. In many cases it is sent at the start of the matter with the engagement pack or uploaded to the client portal.

3. Consider whether the adviser can proceed without it. If confidential information must be obtained or disclosed, or if the adviser is contacting HMRC on the client’s behalf, written authority is often needed before the next stage can move forward.

4. If no document can be found, ask for a fresh copy. The simplest solution is usually for the adviser to resend the relevant form and explain where it should be signed and returned.

5. Make sure the authority matches the task. A general engagement letter may not always be enough if a specific authority is needed for HMRC contact or for another professional in the transaction.

So, the practical issue is not usually whether a complicated legal doctrine applies, but whether the correct paperwork has been issued, signed, and stored in the right place.

Outcome

If a client is asking where the written authorisation document is, the likely answer is that it should be in the original onboarding or engagement paperwork, in the secure portal for the matter, or available directly from the adviser on request. If it cannot be found, the adviser should be asked to resend it and confirm whether anything still needs to be signed before the matter can progress.

Practical Steps

• Check the original engagement letter and any attached forms.
• Review the secure client portal or message inbox for uploaded documents.
• Search earlier emails for attachments containing authority forms or instruction documents.
• Ask the adviser to confirm exactly which authorisation is required.
• Request a fresh copy if the document has not been received or has been misplaced.
• Before signing, make sure the document clearly states who is authorised, for what purpose, and in relation to which matter.

Conclusion

A written authorisation document in an SDLT matter is usually part of the engagement or authority paperwork that allows the adviser to act. If it is not immediately visible, the right course is to check the client file, portal, and earlier correspondence, then ask the adviser to resend it and explain whether any signature is still needed.

Legal References Used

• 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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