What form do you need to authorise a tax adviser to deal with HMRC on your behalf?

Introduction

People often ask what paperwork is needed before a tax adviser can speak to HMRC or deal with a stamp duty matter on a taxpayer’s behalf. The answer usually depends on what stage the matter has reached and whether HMRC requires a formal authorisation. In practice, clients often send over a form they have already completed and then ask whether that is the correct document or whether a separate HMRC authorisation is still needed.

The Question

A taxpayer had already sent a PDF of a form completed earlier in the matter. They wanted to know whether that was the right form for the adviser’s purposes, or whether HMRC required a different authorisation form. They also asked what would happen next if a fresh authority needed to be signed and returned.

Nick’s Explanation

Nick’s reply was brief but clear. He confirmed that the document already sent was helpful, but the next step was still to provide the correct authorisation form for signature if required.

In substance, the position was:

• the form already provided may assist with the file and background information;
• it may not be the same as the formal HMRC authority needed for the adviser to act directly;
• if a separate authority is needed, the adviser will send it to the taxpayer for signature and return;
• once signed, the adviser can proceed with the next steps and further instructions.

This reflects a common distinction in tax matters: a document completed for one purpose is not always enough to authorise an adviser for HMRC dealings.

The Law

HMRC generally requires proper authority before discussing a taxpayer’s affairs with an agent or adviser. The exact mechanism depends on the type of tax, the process being used, and whether the authority is being given through an online agent services process, a paper authorisation, or a specific form connected with a relief, amendment or repayment claim.

For stamp taxes and related HMRC correspondence, the practical issue is usually not a complex point of substantive tax law but one of authority and procedure. HMRC must be satisfied that:

• the taxpayer has appointed the adviser to act;
• the authority covers the relevant tax and matter;
• the form used is the one HMRC accepts for that purpose.

Where a claim, amendment or repayment request is being pursued, HMRC may also require supporting documents in addition to the authority itself.

Analysis

The key point is that not every signed form does the same job.

Step by step, the position is usually as follows:

1. The taxpayer may already have signed a document during the transaction or at an earlier stage of the matter. That document may contain useful information, but it does not automatically give a new adviser authority to deal with HMRC.

2. The adviser must check whether the existing form is:

   • a client care or engagement document;
   • a transaction-related form;
   • an internal questionnaire or fact-find;
   • or an actual HMRC agent authorisation.

3. If it is not the correct HMRC authority, a fresh authorisation will need to be issued, signed and returned.

4. Only once the correct authority is in place can the adviser usually correspond with HMRC fully and progress the matter efficiently.

That is why a response saying that the existing PDF is “helpful” does not necessarily mean it is sufficient. It may help the adviser understand the case file, but HMRC may still insist on its own accepted form of authority.

Outcome

The practical conclusion is simple: a previously completed form may be useful, but it may not be the formal authorisation needed for HMRC. If the adviser says a separate authorisation is required, the taxpayer should sign and return that document before expecting the adviser to take the next procedural steps with HMRC.

Practical Steps

• Ask the adviser to confirm exactly what the existing form is and whether HMRC will accept it.
• Check whether the adviser needs a general agent authorisation, a matter-specific authority, or both.
• Sign and return any fresh authority promptly to avoid delay.
• Keep copies of all forms sent and received.
• Make sure the name of the taxpayer and the details of the tax matter are consistent across all documents.
• If the matter concerns a stamp duty refund, amendment or relief claim, ask whether any supporting papers are also needed in addition to the authority form.

Conclusion

If you have already sent a form to your adviser, that may still be useful, but it is not always the document HMRC needs. The safest course is to wait for the adviser to confirm whether a fresh authorisation is required and, if so, sign and return it promptly so the matter can move forward.

Legal References Used

• HMRC procedural requirements on agent authorisation and taxpayer consent
• HMRC practice relating to authority for agents to correspond on a taxpayer’s behalf

This page was last updated on 22 March 2026.

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