UK HM Revenue and Customs(HMRC) rolled out a new online mandatory registration system for tax advisors. Tax advisers who are paid to interact on behalf of their clients with HMRC are obliged to register online starting from May 18, 2026.
Online registration obligation has different deadlines. The deadline for registration is differentiated by following the precise instructions issued by HMRC, that could be consulted online on the HMRC website. The online registration is set up to become fully operational in the period between May 18, 2026, and March 31, 2027.
Registration is free of charge. The new registration system shall replace a range of previous processes and shall reduce the unnecessary administrative burden on advisers. Advisers can also use the new interactive checker tool to evaluate if they need to register.
Modernising and Mandating Tax Adviser Registration
Modernising and Mandating Tax Adviser Registration(MMTAR) guidance was published on February 17, 2026. Impacted tax advisers need to meet the HMRC’s registration requirements to apply for an agent services account(ASA).
Registration for ASA is the first necessary step for registration. Advisers have three months from the start of their registration window to apply for an ASA. They can continue to interact with HMRC on behalf of their clients:
- during these three months
- while HMRC considers their registration.
Tax advisers who have previously obtained ASA registration don’t need to register again. Tax advisers who are required to register via the new portal, and who don’t meet the requirements, will not be permitted to communicate with HMRC on behalf of their clients.
The advisers who don’t stop here, but move forward with the interaction with HMRC officers, even though lacking online registration, could face financial penalties and other sanctions.
Failing to register could also delay or disrupt services for clients and damage trust with individuals and businesses relying on professional tax support.