Legislation included in the Finance Act 2026 (Part 7 and Schedules 20 and 21) requires businesses interacting with HMRC in respect of another person’s tax affairs to register as a tax adviser with HMRC. HMRC has introduced a new digital registration system for this purpose.

When to register

Businesses have three months from their start date to register with HMRC. The start date is 18 May 2026 unless a later start date applies or the business has an agent services account (ASA). 

The later start dates are as follows: 

• 18 August 2026, for businesses that have a self assessment or corporation tax (ie, an online services account (OSA)), but do not have an ASA; 
• 18 November 2026, for businesses that only provide third-party payroll services on behalf of clients and do not interact with HMRC in any other way; and
• 31 December 2026, for financial services organisations. 

Businesses can continue to interact with HMRC in their three-month registration window and while they wait for HMRC to consider their application. Businesses that do not have an ASA are free to register with HMRC before their start date. 

A business that already has an ASA does not need to take any action yet. HMRC will contact the business through their ASA between 31 December 2026 and 31 March 2027 if more information is required, for example, about the relevant individuals of the business.

Guidance

HMRC has published an interactive tool that businesses can use to check if they need to register with HMRC. Further, HMRC has published a factsheet and high-level guidance on:

• the conditions that must be met to register with HMRC;
• if and when a business needs to register with HMRC;
• the sanctions that may apply; and
• how businesses can appeal against an HMRC decision.

ICAEW understands that further, more detailed guidance will follow. 

ICAEW has published the following articles and podcasts to help businesses understand and meet the new registration requirement:

• HMRC’s agent registration guidance lacks key details
• Tax adviser registration: suspension and sanctions guidance
• Modernising and mandating agent registration