Compliance
Modernising and Mandating Tax Adviser Registration (MMTAR): What Tax Professionals Must Do
New rules phased between May 2026–March 2027 require all paid tax advisers interacting with HMRC to register under the MMTAR scheme—learn who, when, and how.
By NomadicTax Research Team • 6 min read • June 22, 2026
## What is MMTAR?
The **Modernising and Mandating Tax Adviser Registration (MMTAR)** scheme introduces a **mandatory registration requirement** for anyone who is paid to interact with HMRC on behalf of clients. The goal is to improve standards, transparency, and consumer protection in the tax advice market.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Who must register and when?
The rollout is staged to allow different groups to register over time. Key dates:
| Stage | Who | Window Open | Must Meet Conditions |\
|---|---|---|---|\
| 1 | New advisers or those without an Agent Services Account (ASA), or no Self Assessment or Corporation Tax account | **18 May – 18 August 2026** | Must satisfy HMRC’s registration conditions |([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))\
| 2 | Advisers with SA or CT accounts but no ASA | **18 August – 18 November 2026** | Same conditions |([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))\
| 3 | Advisers providing payroll-only services | **18 November 2026 – 18 February 2027** | — |([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))\
| 4 | Those already holding an ASA & financial services organisations | **31 December 2026 – 31 March 2027** | — |([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**, but failing to register by your applicable deadline means you **cannot represent clients to HMRC** and may face sanctions.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## What’s involved and how to prepare
- **Criteria check**: You’ll need your Government Gateway user ID, VAT or company registration numbers (if relevant), UTR for firm, your National Insurance number, etc. Identity verification is required.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Determine if you’re exempt: e.g. volunteering or doing activities that “aren’t tax advice” may avoid this requirement. Customs intermediation might be excluded.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Use the interactive checker tool on GOV.UK to confirm whether you need to register and in which phase. Early action helps avoid disruption.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Impacts on clients and advisers
**For advisers:**
- If you fail to register by your deadline, you lose legal authority to act for clients before HMRC. It could sever ongoing client relationships until proper registration is in place.
- Administrative burden: ensuring record-keeping, compliance with registration criteria, and communication with HMRC. Some advisers must adapt existing agent services accounts or create new ones.
**For clients:**
- Better protection: adviser identities are verifiable, standards are more consistent, and unqualified or unregistered agents can’t legally represent clients.
- Possible short-term disruptions as advisers adjust; important to verify your adviser’s registration status if engaged before deadlines.
## Example scenario
- Jane is a freelance tax adviser who helps clients with personal Self Assessment but does not currently have an Agent Services Account. She must register between **18 May and 18 August 2026**. If she misses that, she can’t represent clients to HMRC for Self Assessment until she has registered under the programme. If she already had an ASA, she’d have later deadlines.([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Action plan for advisers now
1. Use public GOV.UK tools to check your registration status and deadline.
2. If you don’t have ASA or the needed criteria, begin gathering required documents ahead of your rollout window.
3. Update your business processes and contracts to include compliance with MMTAR.
4. Notify clients if changes may affect timeliness or services.
**Bottom line:** MMTAR is a big compliance shift. If you give tax advice for pay and interact with HMRC, register by your deadline — it’s essential to maintain your professional standing and ability to act on behalf of clients.