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. It also provides that the start date, and any transitional rules, will be set out in regulations.

Those regulations have now been made: The Finance Act 2026 (Registration of Tax Advisers) (Appointed Days and Transitional Provision) Regulations 2026, SI 2026/807. The regulations confirm the timetable announced by HMRC in May 2026 for advisers without an  ASA  and set out the process for advisers with an ASA.

Advisers with an ASA 

The process for mandatory registration is determined initially by whether the adviser has an ASA immediately before 18 August 2026.  

If they have, they are treated as if: 

• they had applied to HMRC to be registered; 
• their application was approved by HMRC; and
• they were notified that their registration had effect from 18 August 2026.  

Firms in this group will still need to complete a process when HMRC contacts them – expected to be early 2027 – where they will need to name the firm’s relevant individuals and provide evidence of anti-money laundering (AML) supervision.

Advisers without an ASA 

If the adviser does not have an ASA immediately before 18 August 2026, the window during which they must apply to be registered with HMRC depends on which tranche they fall into: 

The criteria for each tranche are set out below: 

• First tranche: they do not fall within any other tranche.
• Second tranche:
  • they have a self assessment or corporation tax account (ie, an online services account); and
  • they do not fall within the third or fourth tranche.
• Third tranche:
• the only tax adviser activities they carry on between 18th August 2026 and 17th February 2027 are payroll services; and
• they do not fall within the fourth tranche.
• Fourth tranche: Between 18th August 2026 and 31st March 2027:
• their business consists (to a substantial extent) of carrying on regulated activities; or
• their clients are (to a substantial extent) group undertakings in relation to the tax adviser, and one or more of the tax adviser’s group undertakings has a business which consists (to a substantial extent) of carrying on regulated activities.

The definitions applying for this purpose, including for the terms "payroll services", "regulated activities" and "group undertaking", are provided by the regulations.  

Businesses can continue to interact with HMRC in their three-month registration window and while they wait for HMRC to consider their application. An earlier article explains the sanctions that may apply where a business is in breach of the rules.