Compliance
Staying Compliant: UK’s New Rules for Tax Advisers and What They Mean for Clients
From May 2026, UK tax advisers must adhere to new registration requirements under HMRC’s MMTAR reforms—standards that will affect both advisers and the clients relying on them.
By NomadicTax Research Team • 5-8 min read • June 24, 2026
## Overview of the MMTAR Reform in the UK
- **What is MMTAR?** “Modernising and Mandating Tax Adviser Registration” is a set of reforms introduced through Budget 2025. It requires any paid adviser who interacts with HMRC on behalf of clients to register under a **new digital registration system**. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- **Timing & phases**: Registration is rolling out in stages between **18 May 2026** and **31 March 2027**, depending on adviser type—new advisers, those without Agent Services Accounts (ASA), payroll-only advisers, etc. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- **Purpose**: To raise standards, improve consistency, protect consumers, and make it easier to identify legitimate practitioners. Financial investment: £36 million to support this reform. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Implications for Advisors & Their Clients
For **advisers**:
- Must check whether you fall under the registration requirement. Intersection with frequently used roles: self-assessment, corporation tax, payroll, agent services.
- Need to get or use an **Agent Services Account (ASA)** if interacting with HMRC. Those who don’t have one must apply.
- Registration is free, but there may be training or compliance costs to meet eligibility.
- Advisers based **overseas** serving UK clients are also included if interacting with HMRC and getting paid.
For **clients**:
- You should ask your solicitor or tax adviser if they’re registered under the new scheme. A registered adviser means more accountability and easier checks.
- Using unregistered advisers may pose risk: possibly lower standards, or missing remedies if advice proves faulty.
- Fees may shift, especially among junior advisers or small firms adjusting to new processes.
## Practical Steps for Ensuring Compliance
- If you’re an adviser, register under MMTAR as soon as eligible. Don’t wait until the deadline window for your group.
- Make sure your advertising or letterheads clearly identify you as registered (or explain status until registration is complete).
- Keep documentation: proof of qualifications, insurance, registration—for both your own protection and to satisfy clients.
- Train staff about what “interacting with HMRC on behalf of clients” means: it’s broader than just submitting forms—it includes communication, negotiation, and advisory.
## Case Example
John is an accountant in Yorkshire who provides Self Assessment advice and deals with Corporation Tax submissions. As of **18 August 2026**, he is required to register under MMTAR because he interacts with HMRC and has either a Self Assessment or Corporation Tax account but without an ASA. Failing to register by that date could limit his ability to submit returns, or lead to penalties or de-recognition by HMRC when dealing with clients.
Mary, on the other hand, only provides payroll processing advice and does not otherwise interact with HMRC on client affairs. She falls under the late stage (18 Novments-to-Feb) of registration rollout.
## What Clients Should Do
- Ask advisers upfront: “Are you registered under MMTAR?”
- For cross-border taxpayers, verify whether advisers based abroad comply with UK registration.
- Monitor advisers’ published status via HMRC’s register (when live) or ask for proof of registration eligibility.
The MMTAR rollout underscores growing importance of formal credentials in the advice you receive. Both advisers and clients should prepare.