Businesses interacting with HMRC in respect of another person’s tax affairs must register as a tax adviser with HMRC. The requirement is being phased in, with the first cohort of businesses having until 18 August 2026 to register with HMRC.

Each cohort has a three-month window in which to apply for an agent services account (ASA) to register with HMRC. Completing the registration process involves both the firm submitting details and also its relevant individuals providing various confirmations. All of the firm’s relevant individuals must complete their part of the process before the application for an ASA is submitted to HMRC.   

An earlier article provides further details, including the timetable for mandatory registration and links to HMRC’s initial guidance on GOV.UK. This includes confirmation that agents with an ASA do not need to take action until HMRC contacts them to provide details about their relevant individuals.

Detailed guidance

HMRC has now published its mandatory tax adviser registration manual, providing detailed guidance on some aspects of the rules, including:

• which businesses are required to register and when;
• the conditions for registration; and
• how to identify relevant individuals.

The manual also provides confirmation of the transitional arrangements that apply for notifying changes in relevant individuals and the evidence requirements for overseas advisers and relevant individuals.

Notifying changes in relevant individuals 

Registered businesses are required to notify HMRC of changes in relevant individuals, including when a relevant individual leaves the business. HMRC’s guidance (MTAR 20500) confirms that a transitional period applies for businesses registered before April 2027. In this case, the business does not need to notify HMRC of changes to relevant individuals until after April 2027.  

Evidence requirements for overseas advisers and individuals 

HMRC intends to introduce evidence requirements for overseas businesses and overseas relevant individuals and has provided some initial guidance (MTAR 20700) on meeting the requirements. This includes the circumstances in which HMRC will accept alternative forms of evidence.  

The guidance explains that the evidence requirements for overseas businesses and overseas relevant individuals are expected to begin in early 2027, and that HMRC will provide further information in due course. ICAEW has highlighted to HMRC that the guidance needs to be clear about how overseas advisers are supposed to prove a negative – for example, that they have not had a relevant anti-avoidance penalty imposed on them.  

Overseas businesses are advised to register by the relevant deadline, and not to delay their application to register as a tax adviser while they wait for HMRC to publish further information.