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UK’s New Mandatory Registration Requirement for Tax Advisers from May 2026
Starting 18 May 2026, UK tax advisers who interact with HMRC and get paid must register under a new regime, aiming to improve transparency and protect clients.
By NomadicTax Research Team • 5-8 min read • May 15, 2026
## What is MMTAR?
MMTAR stands for **Modernising and Mandating Tax Adviser Registration**, a policy introduced in the UK to improve accountability and raise standards among paid tax advisers. It was first announced in Budget 2025 after a public consultation in 2024.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
Under MMTAR, **any tax adviser who is paid to interact with HMRC on behalf of clients** must register via a new, centralized digital registration system. This requirement is **mandatory**, not optional.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Timeline for rollout
The registration rollout is phased in over several periods from **18 May 2026 to 31 March 2027**, targeting different groups:
- 18 May to 18 August 2026: new advisers or those without an **Agent Services Account (ASA)** and without a Self Assessment or Corporation Tax account.
- 18 August to 18 November 2026: advisers with Self Assessment or Corporation Tax accounts but no ASA.
- 18 November 2026 to 18 February 2027: advisers only offering payroll services.
- 31 December 2026 to 31 March 2027: final group to be phased in.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Who is affected and what’s required
- If you are paid to act for clients before HMRC—filing returns, engaging on self assessment, corp tax, etc—you’re a **tax adviser** and must register, unless exempt.
- Also applies to **overseas advisors** dealing with UK taxpayers.
- Registration requires various identifiers and personal information like UTR, ASA credentials, government gateway ID, VAT number, NI number, AML supervisory body info (if applicable) and verification of identity.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Goals and implications
- **Protecting consumers**: Clients will have clearer recourse and can easily verify registered advisers.
- **Raising standards**: Consistent expectations around conduct and accountability.
- **Transparency and compliance costs**: Advisers must plan for administrative work to register and maintain compliance.
## Action items for personnel
- **Determine whether you fall under the definition** of “tax adviser” under MMTAR—if you get paid and interact with HMRC for clients. If not, you may be exempt.
- **Prepare required documentation ahead of your phase’s registration window.** Missing deadlines may risk non-compliance.
- **Overseas service providers** should ensure systems are in place to comply.
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The MMTAR rollout represents a significant shift in the UK tax advisory landscape. Those who understand the requirements early will help avoid compliance pitfalls and better serve clients.