The first phase of Modernising and Mandating Tax Adviser Registration (MMTAR) closes on 18 August 2026 for new tax advisers, or advisers interacting with HMRC without an agent services account (ASA), Self Assessment or Corporation Tax account.
MMTAR is a single, streamlined digital registration system that is replacing a range of previous processes, making it easier for tax advisers to interact with HMRC. Registration is free and online. Step-by-step guidance and an interactive checker tool are available on GOV.UK to help advisers understand if they need to register and what action they must take. Eligible tax advisers must meet HMRC’s registration conditions to apply for an ASA.
Robert Jones, HMRC’s Director of Intermediaries, said:
"These new requirements will help create a fairer, more transparent tax advice market, support those advisers who meet high standards, and give taxpayers greater confidence in the advice they receive.
“And with one month to go until the first registration deadline, tax advisers who have not yet registered should act now and check the guidance on GOV.UK.”
The government is investing £36 million to help HMRC modernise tax adviser registration and make it simpler for advisers to interact with the tax system as part of its Plan for Growth.
Failing to register could delay or disrupt services for clients and damage trust with individuals and businesses relying on professional tax support.
Tax advisers who miss their relevant registration deadline may face restrictions on their ability to interact with HMRC on behalf of clients. Where advisers continue acting without registering when instructed to stop, HMRC may apply sanctions including financial penalties.





















