UK Mandatory Tax Adviser Registration: Updated Position For In House And Asset Management Tax Functions

Since our original note in January, there have been material developments in the UK’s new mandatory tax adviser registration regime. HMRC has now published guidance, the phased commencement timetable is clearer, and, critically for asset managers and financial institutions, the Government has confirmed a deferral of the regime for financial services businesses until 31 December 2026, following representations led by UK Private Capital.

This update focuses on what these developments mean in practice for in‑house tax teams, asset managers and private capital structures, and where uncertainty remains.

Recap: why this regime matters for in‑house teams

As set out in our January note, the regime is deliberately broad. A “tax adviser” is any organisation which, in the course of a business, assists another person with their tax affairs and interacts with HMRC. This remains unchanged in statute and in HMRC’s guidance.

Crucially, the definition is functional, not professional. Tax does not have to be your core business, and individuals do not need to hold themselves out as advisers. For corporate groups and asset managers, this continues to bring into scope:

• Centralised tax teams acting for multiple entities;
• Asset management tax teams interacting with HMRC in relation to funds, SPVs or portfolio companies; and
• Teams preparing or submitting documents likely to be relied on by HMRC (including SDLT returns and clearance applications).

HMRC guidance: clearer, but not that much clearer

HMRC published its first tranche of formal guidance in February 2026. The guidance confirms several points that are highly relevant for in‑house and asset management functions:

Who must register

• If you interact with HMRC about another person’s tax affairs and are paid, you are considered a tax adviser.
• Registration applies at the entity level, not the individual employee level, although certain individuals must be identified as “relevant individuals” and pass suitability checks.

Key exclusions

• In‑house teams are excluded only where they deal solely with the tax affairs of their own employer or group undertakings.
• The exemption does not extend to non-group entities including:
  • Joint ventures,
  • Funds,
  • Portfolio companies,
  • Bankruptcy‑remote vehicles, or
  • Other non‑group structures common in private capital arrangements.

HMRC’s guidance therefore reinforces the conclusion from January: many in‑house teams will still be caught, even if this was not the original policy intent.

Registration timetable – and the financial services deferral

The registration timetable is now clearer and operates on a phased basis:

• 18 May 2026 – registration opens for those who don’t already have SA or CT accounts, or an existing Agent Services Account (ASA) with HMRC
• 18 August 2026 – registration opens for existing agents with SA or CT accounts but no ASA
• 18 November 2026 – registration opens for advisers providing only third‑party payroll services.

Advisers who already have an ASA do not need to re-register but will be contacted by HMRC, via their ASA, to confirm that the regime's registration conditions are met.

Advisers will have three months from the relevant dates above to apply for registration and will be permitted to interact with HMRC during this period whilst their application is being considered. Note also that advisers in all of the above categories can, if they wish to do so, register from 18 May 2026.

Following sustained industry engagement, the Government has confirmed that:

registration of businesses in the financial services sector will be deferred until 31 December 2026, with a similar three-month period to make their registration application.

This announcement was made via UK Private Capital and applies to asset managers, private capital investment managers and other financial services businesses, while HMRC works through how the regime should apply to these structures in practice.

Although welcome, the deferral raises new questions:

• HMRC has not yet finalised what constitutes a “financial services business” for these purposes, so the precise scope of the deferral remains uncertain.
• It is unclear whether all regulated entities will be included, or whether narrower tests will apply.
• In‑house teams servicing mixed groups (regulated and unregulated) will still need to consider where registration risk arises.

For now, the key point is that most asset managers can treat 31 December 2026 as their operative date (with a three-month window starting at that point), rather than May 2026.

SDLT, payments and “interaction” – key clarifications from HMRC

The WTSG Extraordinary Meeting on Mandatory Tax Adviser Registration (25 March 2026) provides a clear indication of how HMRC is interpreting the regime in practice, particularly for SDLT‑related activity.

The minutes confirm several points that materially increase risk for organisations that had hoped to rely on outsourcing or narrow interpretations of “interaction”:

1. Paying tax counts as “interaction”

HMRC explicitly confirmed that, in its view, paying tax itself constitutes an interaction with HMRC, even where:

• another party prepares and files the return; or
• no substantive correspondence with HMRC takes place.

This significantly broadens the scope of activity that can trigger registration and means that outsourcing tax filings alone will not prevent an obligation to register if the organisation makes payments to HMRC in respect of another person’s tax affairs.

This point is acknowledged in the minutes as controversial alongside a request for urgent guidance. However, it reflects HMRC’s current operational stance, which organisations should assume will be applied in practice.
 

2. Outsourcing does not always remove registration risk

HMRC recorded concerns about:

• conflicting or misleading messaging from outsourcing providers, and
• firms entering outsourcing arrangements under the assumption that this avoids the need to register.

HMRC’s position, as reflected in the minutes, is that:

• registration turns on whether the business interacts with HMRC in relation to a client’s tax affairs, not on who does the mechanical filing; and
• responsibility cannot be contractually displaced by outsourcing.

This reinforces the message in earlier guidance and creates particular exposure for:

• real estate‑heavy groups;
• asset managers overseeing fund‑level tax processes; and
• in‑house legal or tax teams sitting between external advisers and HMRC.
   

3. Relevant individuals – HMRC’s practical approach

The minutes also provide helpful (and slightly softening) commentary on “relevant individuals”, which will be important for larger corporate and asset management groups.

HMRC confirmed that:

• the focus is on individuals with meaningful authority or control over the tax services the business provides;
• the intention is not to capture junior staff or those “simply doing the work”; and
• governance, oversight and decision‑making responsibility is the key lens.

However:

• for entities with five or fewer officers (e.g. small LLPs), all officers may be treated as relevant individuals; and
• for larger organisations, firms must still identify a minimum of five individuals to be subjected to checks, exercising judgement as to who is appropriate.

This aligns with, but usefully elaborates on, the February HMRC guidance. Also helpful was an acknowledgment that there would be an element of grace applied for temporary or minor issues identified in a relevant individual's tax affairs or personal circumstance such as illness which lead to temporary non-compliance.

Practical takeaways for in‑house and asset management teams

1. Do not assume you are out of scope because tax advice is not your business.
2. Map interactions with HMRC now, including who files, signs, makes payments or communicates. Focus on the entities employing the people that carry out the interactions. Note that payment flows matter - where a business pays tax on behalf of another person or entity, HMRC is likely to treat this as interaction.
3. Identify which entities may be “clients”, particularly outside strict group structures. Understanding in detail the extent of the “group undertaking” test (which is wider than a typical tax group) is essential here. Key risk areas emerging from discussions we are having include:
   1. joint venture structures,
   2. asset or property management arrangements,
   3. TSAs,
   4. structures where the entity providing the tax structure sits in a different fund,
   5. fund management where the manager has no ability to appoint directors or otherwise control the fund (e.g. UK investment trusts, some off-shore funds etc)
   6. family offices or LLPs (where tax services are provided to the Ultimate Beneficial Owners or individual partners)
4. Review outsourcing arrangements and provider assumptions carefully – HMRC has been clear that outsourcing is not necessarily a safe harbour.
5. Document governance decisions: whether you think you don’t need to register or you do, keep a record as to why. If you do, document your decisions about who the “relevant individuals” are.
6. For asset managers, note the 31 December 2026 deferral – but use the time to analyse structures and governance – it is not safe to assume that a permanent exclusion will follow.
7. Monitor HMRC guidance closely – further clarification is expected, particularly for financial services.

What to watch next

• Further HMRC guidance on financial services definitions
• Further formal HMRC guidance on the substance of the registration requirement as well as the process for registration, as promised during the WTSG meeting.
• Whether the temporary deferral for financial services results in further legislative change to limit the regime’s application to the financial services sector on a permanent basis.
• If registration seems inevitable, start identifying and preparing the organisation's relevant individuals.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.