• Phase two of the new online registration requirement for tax advisers rolls out.
• Advisers with Self Assessment or Corporation Tax accounts, but without an agent services account (ASA), now need to register.
• Advisers who solely provide professional payroll services do not need to register before 18 November. Financial Services organisations do not need to register before 31 December 2026.
• Mandatory tax adviser registration requirements will protect customers and raise standards in tax advice.

Registration is now open for tax advisers in the second phase of the new Modernising and Mandating Tax Adviser Registration (MMTAR) rollout.

This applies to any advisers with Self Assessment or Corporation Tax accounts, but without an agent services account (ASA). They have until 18 November 2026 to register.

More than 4,000 applications were submitted and over 2,000 accounts created during the first registration window, which targeted the smallest agent audience group.

These mandatory changes are designed to raise standards in the tax advice market, protect taxpayers, and support those who play by the rules.

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.

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 they need to do. Eligible tax advisers must meet HMRC’s registration conditions to apply for an ASA.

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.

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.

Registering on time will help advisers to continue supporting their clients without disruption and maintain the trust that individuals and businesses place in professional tax services.

Advisers who missed the first registration window or who are new entrants to the tax advice market should register as soon as possible. Advisers who submit an application and receive a registration number can still continue to engage with HMRC while their registration is being processed. Access to HMRC’s online services will not be affected in the short term.

HMRC 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 the registration requirement could also face enforcement action, including financial penalties.

Further Information

More information about Modernising and Mandating Tax Adviser Registration (MMTAR) is available on GOV.UK. Eligible tax advisers must meet HMRC’s registration conditions to apply for an agent services account (ASA).

The government is investing £36 million to modernise HMRC’s tax adviser services.

MMTAR registration opened on 18 May 2026 and is being introduced in phases. The first registration window closed on 18 August 2026 and the second registration window is now open until 18 November 2026.

Anyone paid to interact with HMRC on behalf of someone else about their tax affairs is generally considered to be a tax adviser unless an exemption applies.

Tax advisers who already have an ASA do not need to register again. They will be moved to the new digital service by 31 March 2027. HMRC will contact them directly through their account if any additional information is required.

Advisers can continue to interact with HMRC on behalf of their clients while we process their application.

The phased rollout timetable is:

• 18 May to 18 August 2026

  Unregistered tax advisers without an ASA who interact with HMRC on behalf of clients.

• 18 August to 18 November 2026

  Advisers with a Self Assessment or Corporation Tax account who do not have an ASA.

• 18 November 2026 to 18 February 2027

  Advisers who solely provide professional payroll services.

• 31 December 2026 to 31 March 2027

  Financial services organisations. A full definition for this group has already been published.