Businesses that interact with HMRC in respect of another person’s tax affairs are required to register as a tax adviser with HMRC. The requirement is in the process of being phased in. Businesses that did not have an ASA immediately before 18 August 2026 must take action within one of four registration windows. Businesses that had an ASA will also need to follow a process, although key details are yet to be confirmed by HMRC. 

Trusts and trustees 

In recent months, HMRC has updated its detailed guidance to provide clarity for businesses, including in-house tax teams, on whether they are required to register with HMRC. HMRC has now published guidance for trusts and trustees.  

The guidance explains that, where the trustee’s actions consist solely of meeting its tax responsibilities as a trustee, and it is not providing a separate tax-advisory service to a client, the trustee is not required to register with HMRC. This treatment applies to both an individual and to a corporate trustee (including the employees of that corporate trustee) “acting in that capacity”.  

However, HMRC says that this treatment “does not extend automatically to a separate person or organisation that provides tax services to the trustees or the trust under an independent commercial arrangement”.  

Further, HMRC advises that care should be taken when considering the registration requirements of members of the same corporate group as a corporate trustee, as the group-undertaking exemptions (in para 1(1)(f), Sch 20, Finance Act 2026) may or may not apply. The particular facts and registration requirements of each member of the corporate group need to be considered.  

Timetable for registration 

The timetable for registration is explained in detail in an earlier article. Briefly, businesses that do not have an ASA are required to register with HMRC, and must do so within one of four registration windows determined by their circumstances. Where a firm had an ASA immediately before 18 August 2026, HMRC will transition the firm across to the new register. 

We are currently in the second registration window. A firm that has a self assessment or corporation tax account, and does not have an ASA, is required to register with HMRC by 17 November 2026 unless it meets the conditions to register in a later window (for example, it provides payroll services only). 

Firms with an ASA 

Firms that had an ASA immediately before18 August 2026 are treated as if they are registered with HMRC with effect from that date.  However, firms will need still to follow a process when HMRC contacts them. This is expected to be in early 2027.  

It is understood that the transition process will include requiring the firm to: 

• identify its relevant individuals; and 
• provide evidence of anti-money laundering (AML) supervision.