New tax adviser registration rules officially came into force on May 18, 2026, as HM Revenue and Customs began rolling out a digital system that will gradually become mandatory for firms and professionals interacting with the tax authority on behalf of clients. The changes are part of the government’s Modernising and Mandating Tax Adviser Registration (MMTAR) program.
The registration process will be introduced in stages through March 31, 2027. According to HMRC, advisers who fail to register within the required timeframe, or who do not meet the required standards, may eventually lose the ability to act for clients and could face financial penalties if they continue to interact with the agency after being told to stop.
The new framework replaces several existing processes with a single digital registration system. HMRC said the goal is to improve consistency and make it easier to identify legitimate tax advisers while also raising standards across the sector.
According to guidance published on GOV.UK, registration itself will be free, and advisers will be given a three-month window to apply once their registration phase opens. During that period, and while HMRC reviews applications, advisers can continue representing clients.
HMRC Begins Phased Rollout of Adviser Registration System
The first registration phase opened on May 18 for new tax advisers and firms already dealing with HMRC without an Agent Services Account (ASA), Self Assessment account, or Corporation Tax account. Further groups will be added over the next year under a staggered timetable.
From August 18 to November 18, 2026, advisers with Self Assessment or Corporation Tax accounts but without an ASA will be invited to register. Payroll-only advisers will follow between November 18, 2026 and February 18, 2027. The final phase, scheduled between December 31, 2026 and March 31, 2027, will include advisers who already hold an ASA and financial services organizations.
HMRC said advisers already using an ASA do not need to apply again. Existing accounts will automatically move to the new system, although additional information may still be requested through the ASA platform.
According to HMRC’s published guidance, advisers registering under the new system may need to provide Government Gateway credentials, Unique Taxpayer Reference details, company information, VAT registration numbers, and anti-money laundering supervisory information where applicable. Certain individuals and partnerships will also need to complete identity verification checks. The tax authority has also introduced an online tool designed to help organizations determine whether they must register under the new rules.
Industry Reaction Highlights Concerns Over Administrative Burden
The registration requirements were first announced during the government’s 2025 budget and followed a public consultation conducted in 2024. HMRC said respondents broadly supported the introduction of a formal registration system, arguing it would improve accountability and help taxpayers identify legitimate advisers more easily.
Robert Jones, HMRC’s Director for Intermediaries, said advisers should review the guidance early and prepare before their registration period begins. According to HMRC, the reforms are intended to help close the tax gap, support economic growth, and improve confidence in the tax advice market.
Not all professional groups have welcomed the changes. Law Society president Mark Evans described the new requirements as “an additional and unnecessary administrative burden” while discussing how legal firms and conveyancers could prepare for implementation.
Despite those concerns, HMRC has continued to present the reforms as part of a broader effort to modernize oversight of tax advisers. The agency said firms that comply with the registration process will continue operating normally while the transition to the digital system unfolds over the coming months.
