Tax adviser registration enters phase two, with an 18 November deadline

HMRC has opened the second window of its mandatory tax adviser registration scheme, and a fresh group of advisers now has until 18 November 2026 to sign up or risk enforcement action.

Who needs to act now

The rolling programme to bring every paid tax adviser onto a single register has moved into its next phase. On 18 August 2026 HM Revenue and Customs opened the second registration window under its Modernising and Mandating Tax Adviser Registration scheme, known as MMTAR.

This phase is aimed at a specific group: advisers who have a Self Assessment or Corporation Tax account but do not yet hold an agent services account, or ASA. Those advisers now have until 18 November 2026 to register, and HMRC is encouraging them to check whether the requirement applies to them and to submit their application as soon as they can rather than leaving it to the deadline.

Not everyone falls into this window. Advisers who solely provide professional payroll services do not need to register before 18 November, and financial services organisations do not need to register before 31 December 2026. As a general rule, though, anyone paid to interact with HMRC on behalf of someone else about their tax affairs is considered a tax adviser unless a specific exemption applies.

How the first phase went

The scheme is being introduced deliberately in stages, and the opening phase gives a sense of the numbers involved. That first window, which ran from 18 May to 18 August 2026 and targeted the smallest group of agents, drew more than 4,000 applications and led to over 2,000 accounts being created.

HMRC describes MMTAR as a single, streamlined digital registration system that replaces a patchwork of previous processes, with the aim of making it easier for advisers to deal with the department. Registration is free and completed online, and GOV.UK carries step-by-step guidance along with an interactive checker tool to help advisers work out whether they need to register and what to do. Eligible advisers must meet HMRC's registration conditions before they can apply for an ASA. The government is putting £36 million into modernising HMRC's tax adviser services to support the change.

Standards, trust and the stick behind the rules

The stated purpose of the scheme is to lift standards across the tax advice market. Robert Jones, HMRC's Director of Intermediaries, said: “Together, these measures will reinforce trust and transparency across the tax advice market, supporting high standards and helping taxpayers access advice with greater confidence.” He urged advisers in the current group to act promptly, adding: “Now that the second registration phase is open, advisers in the next group should check the guidance on GOV.UK and make sure they register by 18 November 2026.”

HMRC is keen to stress that registering on time keeps advisers working without interruption. Those who submit an application and receive a registration number can carry on dealing with HMRC while their registration is processed, and access to online services will not be affected in the short term.

There is, however, a clear edge to the requirement. HMRC has warned that it may limit an adviser's ability to act on behalf of clients if they fail to register when required. Advisers who continue to operate without completing registration could also face enforcement action, including financial penalties. For a practice that depends on being able to file and correspond with HMRC on clients' behalf, losing that ability would be disruptive in the extreme.

Implications

For advisers, the sensible response is to treat 18 November 2026 as a hard deadline and check their status well ahead of it. The distinction that matters is whether a firm already holds an agent services account: those that do are being migrated to the new digital service by 31 March 2027 and need take no further action, while those without an ASA but with Self Assessment or Corporation Tax accounts are squarely in the current window.

More broadly, MMTAR marks a shift in how HMRC oversees the people who act between taxpayers and the tax system. By requiring registration, backing it with conditions advisers must meet, and reserving the power to restrict or penalise those who ignore it, the department is building a gatekeeping layer around the advice market. For clients, that should eventually mean more confidence that whoever handles their tax is known to and accountable to HMRC. For advisers, it means that being properly registered is fast becoming a basic condition of doing the job at all.