Mandatory registration of tax advisers: what does it mean for you?

The headline for the new rules found in Part 7, Finance Act 2026 is that all tax advisers who interact with HMRC on behalf of their clients must register with HMRC unless a specific exception applies. In this article we will explore who is caught by the term ‘tax adviser’ and what this means for in-house tax teams, particularly for complex organisations involving joint ventures and portfolio companies.

So who is a tax adviser?

The legislation defines a tax adviser as an organisation or individual that, “in the course of a business carried on by it/the individual, assists other persons with their tax affairs“. Such assistance includes giving tax advice and acting as an agent in relation to tax but also providing assistance with “any document that is likely to be relied on by HMRC to determine the other person’s tax position“. A client is simply defined as any person who receives assistance from a tax adviser.

The definition is, patently, very broad and appears to cast a far wider net than capturing the usual third party professional tax advisers, lawyers and accountants. Without more, it would appear that anyone completing an SDLT return or stock transfer form could be caught. It also begs the question of whether in-house tax professionals need to register their own organisation in order to interact with HMRC when providing documents on behalf of group companies or connected joint ventures.

So do I have to register for having an in-house tax function?

The short answer is probably not. Organisations with an in-house group tax function should not have to register as tax advisers with HMRC. There are a few areas of comfort here, the first being an exception in the legislation itself. Where an adviser interacts with HMRC in relation to a client who is a group undertaking in relation to the adviser, this is specifically called out as an exception in Schedule 20, Finance Act 2026. The term “group undertaking” takes its meaning from the Companies Act where it includes parent and subsidiary companies (including sister companies). Therefore, in-house tax functions at the group level should not be required to register just because they are assisting another group subsidiary that could, for internal purposes, be viewed as a “client”.

However, what about where there is no corporate group connection?  For example, where organisations partake in joint ventures where a jointly held entity is subject to 50/50 rights of control and ownership. Or perhaps there is a trust arrangement or complex fund structure where tax advice might be provided to portfolio companies by an investor or fund manager. The answer here is less definitive and largely reliant on HMRC guidance that remains a work in progress.

What we know so far is that HMRC guidance indicates that registration is “only intended to apply where there is a genuine third-party advisory relationship… where there is no genuine third-party advisory relationship [HMRC] does not intend that those businesses should register.” Helpfully, HMRC guidance also states their interpretation of “business” in the tax adviser definition indicates tax advisers are paid for their assistance to clients.  However, where there are inter-company recharges, for example for back-office functions including tax, this may not provide sufficient comfort.

In a bulletin published last month, HMRC suggested that “complex organisational structures” that should not be caught by the registration rules include joint ventures, investment structures (including REITs and managed funds), SPVs and their sponsoring firm, partnership models with multiple LLPs, trusts and their trustees plus transitional advice during mergers and acquisitions (presumably under TSAs when part of a group is sold). However, even though deadline for the first wave of registrations has passed, we still do not have the further clarification promised in guidance. The guidance we do have is consistently caveated with statements such as, “Whether a business is required to register with HMRC will depend on the business’s individual circumstances.” A lot of reliance may therefore need to be placed on HMRC’s published promise in the July bulletin: “Businesses relying on HMRC guidance in good faith to decide that they do not need to register will be treated as compliant, with no sanctions or penalties, even if HMRC later clarifies that the business should register.”

What to do next?

Firstly, in-house tax professionals are recommended to review the rules and make a clear record of their findings in order to demonstrate compliance. HMRC guidance is clear that sanctions under the regime for non-compliance are not intended to punish genuine mistakes and non-compliant taxpayers will be offered the opportunity to take corrective action. A contemporary record will be key to demonstrating that the decision to register, or not, was made in good faith.

Secondly, if the conclusion is that the in-house tax team needs to be registered, don’t panic! Only organisations which are not already registered for corporation tax or self-assessment had to be registered by 18 August. An organisation large enough to warrant an in-house tax team will likely be registered for one of these already and therefore is in the second wave of registrations which need to be completed by 18 November.

Our Tax team is on hand to help you navigate the new mandatory registration of tax advisers regime – please feel free to reach out to us with any questions or concerns.