Tax advisers have just one month left to register under new mandatory requirements imposed by HMRC, with the first phase of the Modernising and Mandating Tax Adviser Registration (MMTAR) scheme closing on 18 August 2026. This deadline applies to new tax advisers or those interacting with HMRC without an agent services account (ASA), Self Assessment, or Corporation Tax account.
What Is MMTAR?
MMTAR is a single, streamlined digital registration system that replaces a range of previous processes, making it easier for tax advisers to interact with HMRC. The registration is free and conducted online. Step-by-step guidance and an interactive checker tool are available on GOV.UK to help advisers determine if they need to register and what action to take.
Government Investment and Official Warning
The government is investing £36 million to help HMRC modernise tax adviser registration and simplify interactions with the tax system as part of its Plan for Growth. Robert Jones, HMRC’s Director of Intermediaries, issued a stark warning alongside the press release: “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.” He added: “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.”
Consequences of Missing the Deadline
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.
Next Steps for Advisers
Advisers unsure about their obligations are urged to use the online checker tool and complete registration before the 18 August cutoff. The MMTAR system is part of a broader effort to improve transparency and fairness in the tax advice market, ensuring only qualified and registered professionals can represent clients before HMRC.
