HMRC opens second phase of mandatory tax adviser registration

HM Revenue & Customs (HMRC) has launched the second phase of its Modernising and Mandating Tax Adviser Registration (MMTAR) rollout. This initiative introduces a streamlined digital registration system designed to replace multiple previous processes and improve interactions between tax advisers and the agency.

The current phase requires advisers who hold Self Assessment or Corporation Tax accounts but lack an agent services account (ASA) to register by 18 November 2026. Financial services organisations have until 31 December 2026 to comply, while those providing solely professional payroll services are exempt from this specific deadline.

HMRC stated that the mandatory changes aim to raise standards within the tax advice market, protect taxpayers, and increase transparency. Failure to register may result in HMRC limiting an adviser’s ability to act on behalf of clients or pursuing enforcement actions, including financial penalties. Registration is free and can be completed online via the GOV.UK website.