Compliance
Modernising Tax Advice: What Tax Advisers Need to Know About HMRC’s New Registration Requirements
From 18 May 2026 UK tax advisers will be subject to new registration rules under the MMTAR initiative—this article explains who’s affected, what’s required, and how to avoid disruption for your clients.
By NomadicTax Research Team • 5-8 min read • May 15, 2026
## What is MMTAR?
**MMTAR** stands for *Modernising and Mandating Tax Adviser Registration*. This policy introduces a **legal requirement** for anyone paid to interact with HM Revenue & Customs (HMRC) on behalf of a client to register with HMRC and meet certain minimum standards. Originally announced as part of the Budget 2025, it’s been under consultation and will rollout in phases. ([gov.uk](https://www.gov.uk/government/publications/modernising-and-mandating-tax-adviser-registration-with-hmrc?utm_source=openai))
## Who is affected and when?
| Adviser Group | Registration Window | Key Details |
|---|---|---|
| New advisers and those without an Agent Services Account (ASA), Self Assessment or Corporation Tax account | 18 May to 18 August 2026 | Must begin registration; transition applies for three months per window. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) |
| Advisers with SA or CT account but without ASA | 18 Aug to 18 Nov 2026 |
| Those only providing payroll services | 18 Nov 2026 to 18 Feb 2027 |
| Financial services orgs and advisers already with ASA | 31 Dec 2026 to 31 Mar 2027 |
Advisers have **three months** from their window’s start to apply—meanwhile, they can still act on clients’ behalf. Failure to register after your deadline exposes you to losing the ability to submit on behalf of clients, and potentially facing sanctions. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## What you need to do now
- Use the interactive checker on GOV.UK to confirm whether you qualify as a “tax adviser” under the rules. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Gather required information: UTR, ASA (if you have one), VAT registration, National Insurance number, company registration number, etc. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Ensure compliance in your own tax affairs—applications could be rejected if tax returns aren’t up to date or compliance requirements aren’t met.
- Check for exemptions: charities, voluntary sector, and those who do not provide paid tax advice but volunteer may be exempt. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
## Implications and examples
**Small practice example:** Jane runs a small tax consultancy. If she communicates with HMRC in Self Assessment on her clients’ behalf, she must register under MMTAR during the first phase starting 18 May 2026. She doesn’t currently have an ASA—this means she must apply for one. She uses the guidance tool on GOV.UK and realises she’s in the first window. She applies promptly to avoid disruption around filing deadlines.
**Overseas adviser example:** A tax adviser based outside the UK advising UK clients must register if they are paid and interact with HMRC on their behalf. Without registration, they cannot act for those clients or file on their behalf.
## Actionable insights
- Start preparing **before** your registration window opens. Even though registration is free, delays could cost clients if advice cannot be submitted.
- Review your existing Agent Services Account—some advisers already have ASA and may merely require migration to the new digital system.
- Update your systems and compliance—ensure staff are aware of documentation required and new minimum standards.
## Why this change matters
This isn’t just administrative. It's a quality and trust initiative. Ensuring advisers are identifiable, meeting standards, and acting lawfully protects clients—and also helps HMRC reduce fraudulent or low-quality advice. For honest practitioners it levels the playing field.
**Published:** Early implementation rolling out from 18 May 2026.
**Category:** Compliance