Compliance
UK Tax Advisers Must Register Under New HMRC Rules – What You Need to Know
From 18 May 2026, UK tax advisers who interact with HMRC must register under the Modernising and Mandating Tax Adviser Registration (MMTAR) regime – here’s how to prepare and avoid penalties.
By NomadicTax Research Team • 5-8 min read • May 19, 2026
## Overview
As of **18 May 2026**, HM Revenue and Customs (HMRC) is enacting a **new registration requirement** for all paid tax advisers who interact with HMRC on behalf of clients. This change comes under the Modernising and Mandating Tax Adviser Registration (MMTAR) programme, announced in the UK Budget 2025.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) It replaces multiple existing agent or adviser identification processes with a **single, streamlined digital registration**.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Who Needs to Register
Tax advisers who need to register include anyone, whether based in or outside the UK, paid for:
- Interacting with HMRC on behalf of clients,
- Preparing or filing Self Assessment or Corporation Tax returns,
- Offering tax advice as an agent (unless exempt).
Exemptions apply for those not providing advice commercially, or those in specific sectors and activities (e.g. certain voluntary sector entities or customs brokering).([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Phased Roll-Out Schedule
The registration requirement will be **phased in** across several cohorts:
| Phase | Who Must Register | Start Date |
|---|--------------------|-------------|
| Phase 1 | New tax advisers, or those interacting without an Agent Services Account (ASA), or without Self Assessment/CT accounts | 18 May 2026 |
| Phase 2 | Advisers with SA or CT accounts but without an ASA | 18 August 2026 |
| Phase 3 | Advisers who only provide payroll services | 18 November 2026 |
| Phase 4 | Remaining advisers, to be completed by 31 March 2027 | 31 December 2026 to 31 March 2027 window |([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## What Registration Requires
To register under MMTAR, advisers will need to have:
- Government Gateway credentials,
- Unique Taxpayer Reference (UTR) for their agent firm,
- Relevant identity documents: National Insurance number, date of birth, company registration and VAT numbers if applicable,
- Information regarding anti-money laundering supervisory body if applicable.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
Registration is **free**. HMRC is releasing guidance and tools including a checker to determine if someone qualifies.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Implications & Action Steps
**Why this matters:**
- Enhances **regulatory oversight**, helps combat malpractice in tax advice,
- Protects taxpayers by increasing standards and consistency,
- Enables HMRC to better enforce compliance.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
**Risks for non-registration:**
- Advisers may lose ability to represent clients,
- Could face fines or professional censure,
- Loss of trust and business reputation.
**Your action plan:**
1. Determine if you fall under the registration requirement as of 18 May,
2. Collect necessary documents and sign up for Government Gateway if you haven’t,
3. Monitor HMRC guidance for updates,
4. Notify clients of your registration status for transparency.
## Summary
The HMRC’s MMTAR registration reform is a major change for tax advisers in the UK. By streamlining processes and standardising registration, it aims to shore up standards across the profession. If you're advising, acting on client’s tax affairs, or interacting with HMRC, make **first registration steps by 18 May 2026 (if applicable to you)**.