Introduction
From 18 May 2026, any tax adviser who is paid to interact with HMRC on behalf of clients must register for an Agent Services Account (ASA) under the Modernising and Mandating Tax Adviser Registration (MMTAR) policy. This requirement applies to both UK-based and overseas advisers. (gov.uk)
Who Needs to Register & When
Registration is being phased in by adviser category, with 3-month windows for each:
| Adviser Type | Registration Window |
|---|---|
| New advisers, or those without an ASA, Self Assessment, or Corporation Tax account | 18 May – 18 August 2026 (gov.uk) |
| Advisers with Self Assessment or Corporation Tax account but no ASA | 18 August – 18 November 2026 (gov.uk) |
| Those only providing payroll services to third parties | 18 November 2026 – 18 February 2027 (gov.uk) |
| Financial services firms (w/o ASA) | 31 December 2026 – 31 March 2027 (gov.uk) |
Minimum Standards & Conditions
To be able to register, advisers must meet HMRC’s registration conditions which include:
- Having appropriate anti-money laundering (AML) supervision if required (gov.uk)
- Not being disqualified as a director in the UK or overseas (gov.uk)
- Providing evidence of identity details; overseas advisers may need notarised and translated documents (gov.uk)
Steps to Take Now
- Evaluate whether you are considered a tax adviser by HMRC: remunerated help with someone else’s UK tax affairs, including returns, correspondence, claims, etc. (gov.uk)
- If you lack an ASA, prepare to apply when your tranche’s window opens. You will have 3 months from that date to register. (gov.uk)
- Review if you meet minimum standards. If not, take steps to remedy (e.g. registering for AML supervision, ensuring identity documents are in order) before your registration window.
- If advising clients outside your scope due to missing registration, plan an exit or handover: clients might lose representation privileges.
Implications for Clients
Clients should:
- Check whether their tax adviser has an Agent Services Account once their adviser’s window closes.
- Be cautious if the adviser has not registered—HMRC may refuse to deal with them.
- Ask questions about adviser’s credentials, especially regarding AML supervision.
Compliance & Sanctions
Failure to comply can lead to:
- Being unable to access HMRC systems on clients’ behalf.
- Potential suspensions or penalties if acting while unregistered or failing to meet standards. (gov.uk)
Case Example
Sarah runs a small advisory firm based in Manchester, helping clients with Self Assessment and Corporation Tax. She doesn’t yet have an Agent Services Account. Her registration window is 18 August – 18 November 2026. If she misses this, she can’t legally interact with HMRC as a paid adviser on these matters. Worse: if she still files returns, she could face sanctions or loss of access to HMRC support tools.
Conclusion
The UK’s introduction of mandatory tax adviser registration is a significant change aimed at improving clarity and trust in the tax advice market. Those affected must act proactively: identify whether they need to register, ensure they meet standards, and apply during the correct window. For clients and advisers alike, this policy raises the baseline for accountability and professionalism in tax advice.