• Registration deadline for new tax advisers is 18 August 2026.
• Tax advisers who still need to register should act now to avoid disruption to their ability to support clients.

Tax advisers have one month left to register under new mandatory requirements designed to raise standards in the tax advice market, protect taxpayers, and support those who play by the rules.

HM Revenue and Customs (HMRC) is encouraging anyone who has not yet registered to check if they need to and submit their application as soon as possible.

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.

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).

MMTAR registration opened on 18 May 2026 and is being introduced in phases. This first registration window closes on 18 August 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.

Advisers who already have an agent services account (ASA) do not need to register again at this stage. HMRC will contact them directly through their ASA if any additional information is required as they move to the new digital system.

The phased rollout timetable is:

• 18 May to 18 August 2026
  New tax advisers, or advisers interacting with HMRC without an agent services account (ASA), Self Assessment or Corporation Tax account.
• 18 August to 18 November 2026
  Advisers with a Self Assessment or Corporation Tax account, but without an agent services account.
• 18 November 2026 to 18 February 2027
  Advisers who solely provide payroll services.
• 31 December 2026 to 31 March 2027Those who already have an ASA, and financial services organisations. A full definition for this group has already been published

SOURCE: GOV