HMRC mandatory tax adviser registration: what firms need to know

If your firm interacts with HMRC on behalf of clients and is paid for doing so, you will be legally required to register as a tax adviser with HMRC from 18 May 2026. 

This is not a requirement aimed solely at specialist tax practices. It will likely apply to conveyancers, private client solicitors, corporate lawyers, family practitioners, and potentially many others – regardless of whether your firm has ever described itself as providing tax advice.

This article explains what the requirement means, who is affected, the key dates and steps your firm must take, the consequences of non-compliance, and the broader risk management implications for law firms arising from this new requirement.  

Why is this happening?

The mandatory registration regime has been introduced by the Finance Bill 2025-26 and forms part of HMRC's wider programme to raise standards in the tax advice market. HMRC has invested £36 million to modernise its registration infrastructure, replacing the current fragmented, often paper-based registration processes with a single digital route via the Agent Services Account (ASA) system.

The government’s stated purpose is to ensure that all advisers who interact with HMRC on behalf of clients meet minimum standards, enabling HMRC to monitor and, where necessary, exclude those who are "objectively unable" to meet its standards for agents. Following a consultation in October 2024, stakeholders broadly supported mandatory registration as a mechanism to create a fairer market and deter unscrupulous operators. Crucially for law firms, despite strong opposition from both the Law Society and the Council for Licensed Conveyancers, solicitors and licensed conveyancers were not exempted from the regime.

Will this apply to your firm?

The definition of "tax adviser" in the legislation is deliberately broad. It captures any firm or individual that, as part of its business, assists others with their tax affairs, which is taken to include:

• making, or assisting with, claims or elections in connection with a client's tax affairs;
• submitting information or returns to HMRC on a client’s behalf;
• communicating with HMRC regarding a client's tax position; and
• providing assistance with any document likely to be relied on by HMRC to determine a client's tax position, even where tax is incidental to the wider service being provided.

The practical consequence is that the test is not whether your firm considers itself a tax adviser in any conventional sense, but simply whether it interacts with HMRC about a client's tax affairs and receives payment for that work. If it does, registration will be required.

Which areas of practice are affected?

An article by Kennedys LLP suggests that the following practice areas most directly affected will likely include:

Conveyancing

The submission of a Stamp Duty Land Tax (SDLT) return on behalf of a client is sufficient to bring a firm within scope, even where no tax advice whatsoever is being provided. 

Private client

Firms dealing with inheritance tax, trust administration, and estate tax compliance.

Family

Work involving capital gains tax, trust taxation, maintenance and lump sum orders wherever HMRC interaction occurs.

Corporate and commercial

Corporate transactions involving tax filings, and any VAT or PAYE queries directed to HMRC on a client's behalf. 

Litigation

Contentious tax work, including dispute resolution involving HMRC.

The list is not exhaustive. As a general principle, any practice area in which a fee-earner communicates with HMRC on behalf of a client should be assumed to be in scope unless there is a clear exemption.

Who will be exempt?

The legislation does provide some exclusions. Firms will not need to register if they: 

• only deal with their own tax affairs or those within their own company group; 
• provide tax advice services for free (for example, charitable services); 
• interact with HMRC because the law requires it even if paid (for example, certain insolvency practitioners or pension firms); or 
• only provide payroll or tax software for clients to use without themselves interacting with HMRC. 

In-house tax teams acting only for their employer are also excluded.

These exclusions are relatively narrow. Most firms that carry out any of the practice areas set out above should assume they will be required to register.

In each case, firms will have a three-month transition window from their registration date during which they may continue to interact with HMRC on behalf of clients while their application is being processed. Firms that already hold an agent services account will not need to re-register, but HMRC will contact them through their existing account to seek confirmation of compliance with the new conditions.

What will registration involve?

Registration takes place at the level of the legal entity – i.e. the firm itself, rather than individual fee-earners. However, firms are required to identify and provide information about "relevant individuals" as part of the registration process. These are individuals who:

• are officers of the business, including partners in a partnership, members of an LLP, and directors of a company; and/or
• are employees who exercise control or significant influence over the firm's tax-related work, or perform activities falling within the definition of tax adviser functions.

The question of who qualifies as a relevant individual is one area where detailed HMRC guidance remains outstanding. Particular uncertainty surrounds how the relevant individual concept applies in larger firms. Firms will need to work through their management structures carefully, and should err on the side of caution until further guidance is published.

Both the firm and each relevant individual will need to satisfy HMRC's registration conditions. These include:

• no outstanding tax returns or amounts of tax due (for the firm and each relevant individual);
• no current HMRC decision to refuse to deal with the firm or any relevant individual;
• no current anti-avoidance sanctions or stop notices;
• no relevant unspent convictions for fraud or tax offences;
• not being formally insolvent or disqualified from acting as a director; and
• compliance with AML supervision requirements – the firm must demonstrate it is appropriately supervised for anti-money laundering purposes (which for SRA-regulated firms will be the SRA for the time being, pending the move over to the FCA for AML regulation).

How to register

HMRC has now published details of how to register on its website, as well as a useful tool to check whether your firm needs to register (although most firms will need to do so). 

You register by applying for an Agent Services Account (ASA). In order to apply, you will need the following information to hand: 

• a Government Gateway user ID and password (if you do not already have an account you can create one on HMRC’s sign-in page); 
• the Unique Taxpayer reference (UTR) for your firm (you will be assigned an UTR upon creating a Government Gateway account);
• the postcode associated with your UTR; 
• your company registration number (if you have one); 
• your VAT registration number (if you have one); 
• the name of your anti-money laundering supervisory body (the SRA) and evidence of your supervision; and 
• the names and contact details of any relevant individuals working for the business registering. 

HMRC has not confirmed how long the registration process will take, but has confirmed that firms will be able to interact with HMRC on behalf of clients in the usual manner whilst the application is being processed. 

Conclusion

HMRC's mandatory registration regime is a significant development for the legal sector, and one that has arrived with less preparation time, and less detailed guidance, than the profession would have wished for. But the framework is clear enough to start acting on now. 

Firms that treat this as a background administrative matter and leave action until the last minute will be exposed to precisely the kind of operational, regulatory, and reputational risk that good risk management exists to prevent. The immediate steps required are straightforward, so the time to take them is now.