Tax advisers have one month left to register under new HMRC requirements designed to change how paid agents deal with the department on behalf of clients.
The first phase of Modernising and Mandating Tax Adviser Registration closes on 18 August 2026. It applies to new tax advisers, or advisers who interact with HMRC without an agent services account, Self Assessment account or Corporation Tax account.
HMRC said advisers who still need to register should check the guidance and submit an application as soon as possible to avoid disruption. Registration is free and online, with step-by-step guidance and an interactive checker available on GOV.UK.
The new system is intended to replace a range of previous processes with a single digital registration route. Eligible advisers must meet HMRC registration conditions before applying for an agent services account.
HMRC said anyone paid to interact with the department on another person’s tax affairs is generally treated as a tax adviser unless an exemption applies. Advisers who already have an agent services account do not need to register again at this stage, and HMRC will contact them directly through that account if further information is needed.
The department warned that missing a relevant deadline could delay or restrict an adviser’s ability to act for clients. It said sanctions, including financial penalties, may apply where advisers continue acting after being instructed to stop because they have not registered.
The government is investing £36 million in the programme as part of work to modernise tax adviser registration and make interaction with the tax system simpler. MMTAR opened on 18 May 2026 and is being introduced in phases.