Compliance
Modernising Tax Adviser Registration in the UK: What Firms Must Know
From 18 May 2026, all paid tax advisers who interact with HMRC must register under new rules – here’s how to assess your timing, obligations, and actions.
By NomadicTax Research Team • 5-8 min read • June 13, 2026
## What is Mandatory Tax Adviser Registration (MMTAR)?
- **MMTAR** is a government initiative requiring anyone *paid to interact with HMRC about someone else’s tax affairs* to register and meet minimum standards. This replaces older, fragmented processes. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- The **Agent Services Account (ASA)** is the new digital system tax advisers will use. Even if you're based overseas, if you advise UK taxpayers and interact with HMRC on their behalf, you're in scope. ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
## Phased Roll-out: When You Must Register
| Group | Registration window | What counts as interaction |
|---|---|---|
| New advisers or those without an ASA, or without existing Self Assessment or Corporation Tax accounts | **18 May – 18 August 2026** | Any paid role interacting with HMRC (returns, payments, communications) ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) |
| Advisers with Self Assessment or Corporation Tax account but no ASA | **18 August – 18 November 2026** ([gov.uk](https://www.gov.uk/hmrc-internal-manuals/mandatory-tax-adviser-registration/mtar10800?utm_source=openai)) |
| Advisers who *only* do payroll services for clients | **18 November 2026 – 18 February 2027** ([gov.uk](https://www.gov.uk/hmrc-internal-manuals/mandatory-tax-adviser-registration/mtar10800?utm_source=openai)) |
| Financial services organisations (if applicable) | **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)) |
Advisers must register during their window; they have three months from that window’s start. Even before their window opens, advisers **can apply early** and begin interacting via HMRC once applications are submitted. ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
## Who Needs to Register (and Who Doesn’t)
**In scope when being paid and interacting with HMRC:**
- Tax advisers, accountants or legal professionals representing clients.
- Firms doing land transaction returns or payments to HMRC for clients (even via third party software). ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
**Out of scope:**
- Those who do *not get paid* (e.g. volunteers, charities) or making submissions solely for themselves or their employer group. ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
- Specific tax-related services like customs intermediaries or some VAT representatives depending on context. ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
## Responsibilities and Risks
- Register via the **online HMRC service**, including submitting anti-money laundering supervision status first. ([gov.uk](https://www.gov.uk/government/publications/mandatory-tax-adviser-registration-communications-resources/fact-sheet?utm_source=openai))
- Ensure relevant individuals in the firm (those who organise or manage tax adviser services) are identified and meet checks. ([gov.uk](https://www.gov.uk/government/publications/mandatory-tax-adviser-registration-communications-resources/fact-sheet?utm_source=openai))
- Failure to register within your window — or act when directed to stop — could lead to sanctions, loss of ability to interact with HMRC, or financial penalties. ([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 Firms and Advisers
1. **Self-assess** if you're a tax adviser under the new definition (paid, represents clients, interacts with HMRC). Use HMRC’s online checker. ([gov.uk](https://www.gov.uk/guidance/check-if-and-when-you-need-to-register-as-a-tax-adviser-with-hmrc?utm_source=openai))
2. **Mark your registration window** and plan to apply within three months from its start. Busy periods or large client workloads shouldn’t be ignored.
3. **Collect documentation**: proof of AML supervision, identity documents, firm registration details.
4. **Assign relevant individuals** for checks – know who will be identified and what the checks involve.
5. **Review all interactions with HMRC** (even software, APIs, filing services) to ensure compliance post-registration.
## Example Scenarios
- A small accountant who submits Self Assessment returns and files VAT for clients, but has never had an ASA: will need to register between **18 August and 18 November 2026**.
- A freelance adviser providing payroll services only: registration window opens **18 November 2026**.
- A legal professional helping clients with SDLT returns: paid service + submits returns = must register in first tranche.
**Bottom line**: if you're paid and dealing with HMRC on behalf of others, this affects you. Don’t wait until the deadline – start preparing now.