Compliance

How the UK’s New Mandatory Tax Adviser Registration Affects You

Starting 18 May 2026, tax advisers in the UK must register under new HMRC rules—this article explains who needs to register, what changes, and how it impacts clients and entities alike.

By NomadicTax Research Team • 5-8 min read • May 20, 2026

## What is the New Registration Requirement? From 18 May 2026, the UK government has introduced a **new requirement for tax advisers who are paid to interact with HM Revenue & Customs (HMRC) on behalf of clients**. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) This is part of the **Modernising and Mandating Tax Adviser Registration (MMTAR)** initiative, a policy to ensure reliable and standardized tax advice by requiring all paid tax advisers working with HMRC to register. ([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 phased: - **From 18 May to 18 August 2026**: New advisers or those interacting with HMRC without an Agent Services Account (ASA). ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) - **18 August to 18 November 2026**: Those with Self Assessment or Corporation Tax accounts, but without an ASA. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) - **18 November 2026 to 18 February 2027**: Advisers offering payroll services only. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) - **By 31 March 2027**: Full rollout completion. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) There are exemptions—for instance, volunteers or those not acting as a business. Overseas advisers working on behalf of UK clients are also included. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) ## Implications for Clients & Entities For individuals and businesses using paid tax advice: - **Improved reliability & accountability**: Registered advisers must meet certain qualifications, making it easier to verify competence and recourse in case of poor advice. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) - **Risk of using unregistered advisers**: Advice from someone not compliant with registration may carry reputational risk, or potentially expose clients to errors or penalties. - **Cost & administrative burden**: Advisers will need to collect and submit identity-related information; some firms need to adjust their processes. However, registration is **free**, and HMRC is investing £36 million to modernize and simplify the system. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai)) ## Practical Tips for Entities - If you are engaging tax advice services, ask your adviser whether they are or will be registered under MMTAR. - Advise your adviser to start the registration process early—especially if in one of the earlier cohorts (e.g., new advisers or those lacking an ASA account). - Businesses maintaining tax advisers should review contracts: ensure that adviser responsibilities and compliance with HMRC registration are clear. - Keep audit trails: identity docs, ASA confirmation, registration notices in case questions arise during the transition. ## Example Scenario A tech startup engaging a freelance UK-based accountant to file its Corporation Tax returns must ensure the accountant is registered with HMRC under MMTAR by **their designated cohort date** – likely between **18 August and 18 November 2026**, depending on whether the accountant already has or needs an ASA and/or filing roles. Failure to do so might trigger warning letters or risk from HMRC if the adviser is unregistered. ## Summary The MMTAR initiative signals the UK’s commitment to elevating standards in the tax advice market. For entities and clients worldwide who engage UK-based advisers, understanding and verifying registration will become part of due diligence soon—and avoiding disruption depends on awareness and early action.