Compliance
Modernising Tax Adviser Registration: What Agents and Clients Must Know
From **1 April 2026**, all paid tax advisers who interact with HMRC on behalf of clients must register and meet new minimum standards under the MMTAR reforms—here’s who must register, when, and how to comply.
By NomadicTax Research Team • 5-8 min read • August 31, 2026
## The MMTAR Reform: What Is It?
Modernising and Mandating Tax Adviser Registration (**MMTAR**) is a HMRC initiative that requires all tax advisers paid to interact with HMRC on behalf of clients to **register digitally**, meet minimum standards, and maintain eligibility. The measure has been in place **from 1 April 2026**, with a transition period of at least three months. ([gov.uk](https://www.gov.uk/government/publications/modernising-and-mandating-tax-adviser-registration-with-hmrc/requirement-for-tax-advisers-to-register-with-hmrc-and-meet-minimum-standards?utm_source=openai))
The reforms aim to raise standards across the sector, improve transparency for taxpayers, reduce malpractice, and ensure that advisers are accountable. ([gov.uk](https://www.gov.uk/government/publications/modernising-and-mandating-tax-adviser-registration-with-hmrc/requirement-for-tax-advisers-to-register-with-hmrc-and-meet-minimum-standards?utm_source=openai))
## Phased Rollout: Who, When
| Phase | Which advisers must register | Deadline |
|---|---|---|
|Phase 1: New advisers or those without ASA/Self Assessment/Corp Tax accounts|18 May–18 Aug 2026 ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))|
|Phase 2: Advisers who have SA or Corp Tax accounts but **without** agent services account (ASA)|18 Aug–18 Nov 2026 ([gov.uk](https://www.gov.uk/government/news/second-registration-window-now-open-for-tax-advisers?utm_source=openai))|
|Later Phases: Payroll-only advisories; Financial Services organisations|18 Nov 2026–March 2027 etc. ([gov.uk](https://www.gov.uk/government/news/second-registration-window-now-open-for-tax-advisers?utm_source=openai))|
## Minimum Standards & Registration Requirements
- Advisers must meet HMRC’s **standards for agents**, including adequate knowledge, anti-money laundering supervision, professional indemnity, etc. ([gov.uk](https://www.gov.uk/government/publications/modernising-and-mandating-tax-adviser-registration-with-hmrc/requirement-for-tax-advisers-to-register-with-hmrc-and-meet-minimum-standards?utm_source=openai))
- Both UK and foreign-based advisers interacting with UK clients must register. For overseas advisers, extra evidence may be needed (e.g. identity, certifications, translations). ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Failure to register when required may result in sanctions, not being able to act for clients, or fines. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## What This Means for Clients of Tax Advisers
- Ensure your adviser is **registered** under MMTAR and holds an **Agent Services Account (ASA)**. It’s valid to ask for their registration number.
- If your adviser fails to meet requirements, they may be **unable** to act for you or represent you to HMRC.
- Registered advisers will likely need to observe stricter compliance and maintain supervision credentials; this may raise their costs, hence their fees.
## Practical Steps for Advisers and Clients
1. **Advisers** should review the schedule and register in their correct window to avoid disruption.
2. **Clients** should confirm adviser registration status and whether they meet HMRC’s standards.
3. Both should maintain clear documentation—proof of adviser’s qualifications, supervisory body membership, and compliance.
4. For overseas advisers, ensure you have certified documents ready.
## Example Situation
- *Sarah*, an accountant with Self Assessment and Corporation Tax accounts but without ASA: She falls in Phase 2 and must register by **18 November 2026** to comply.
- *Leo*, a payroll bureau only providing payroll services: his window opens later (from November 2026 onward), so he has more time, but must monitor guidance.
This reform signals HMRC’s intention to increase trust in the tax advice market. For both advisers and clients, understanding the schedule, registration conditions, and minimum standards is now essential.