In our February article “Interacting with HMRC? Registration Will Soon Be Mandatory“, we explored the government’s intention to introduce a mandatory registration regime for those interacting with HMRC on behalf of clients. At that stage, the direction of travel was clear, but many of the practical details — particularly around timing and implementation — remained uncertain.
That position has now changed. HMRC has published a defined timetable and provided further clarity on how the registration process will operate in practice. For solicitors’ firms, particularly those engaged in conveyancing, private client and corporate transactional work, this is no longer a future compliance issue. It is an immediate operational requirement that must be understood, planned for and implemented during early 2026.
Why This Still Matters for Solicitors
It is worth briefly revisiting the scope of the regime, because one of the consistent risks for law firms is the assumption that it is directed solely at specialist tax advisers. That is not the case. It applies to any business that interacts with HMRC in relation to a client’s tax affairs.
For solicitors’ firms, this captures a broad range of everyday activities. Submitting SDLT returns, corresponding with HMRC on inheritance tax matters, assisting with disclosures or dealing with tax aspects of corporate transactions will all fall within scope. In practice, many firms that would not describe themselves as “tax advisers” will nevertheless be required to register.
This makes the timetable particularly significant. It is not limited to niche practices but applies across much of the legal sector.
The Implementation Timetable
The most important development is the confirmation that, following enactment of the Finance Act 2026 (which received Royal Assent on 18 March 2026), from 18 May 2026, firms will be able to register using HMRC’s new online service. This marks the formal commencement of the regime and the point at which registration becomes a legal requirement for the first group of firms.
HMRC has adopted a phased approach to mandatory compliance, recognising that firms interact with HMRC in different ways and at different levels of complexity. The timetable works as follows:
- Firms that do not currently have an Agent Services Account (ASA) and do not have an existing Self-Assessment or Corporation Tax account must register from 18 May 2026.
- Firms that already interact with HMRC through an existing Self-Assessment or Corporation Tax account (but do not have an ASA) must register by 18 August 2026 – although they can register from 18 May if they wish.
- Payroll-only service providers — those that interact with HMRC solely to provide third-party payroll services and in no other way — must register by 18 November 2026.
For most solicitors’ practices without an existing ASA, the critical deadline will therefore be 18 August 2026, with the option to register early from 18 May 2026.
HMRC has also introduced a transitional period of three months from each firm’s relevant registration date. During this period, firms may continue to act for clients while completing their registration and while HMRC processes applications. This provides a degree of flexibility, but it should not be treated as a reason to delay. Firms that leave registration until the end of the transitional window risk operational disruption at exactly the wrong moment.
Firms With Existing HMRC Agent Services Accounts
A key question for many solicitors’ firms is whether they will need to register from scratch, particularly where they already operate an Agent Services Account.
According to HMRC’s published guidance, firms that already have an ASA will not need to register again through the new online service. Instead, HMRC will contact those firms through their existing ASA when it needs further information to check that they meet the conditions for registration. In effect, existing ASA holders will be moved to the new register via a lighter-touch transition process at HMRC’s instigation, rather than being required to submit a fresh application.
This is a meaningful distinction from the position of firms without an ASA. That said, holding an ASA does not amount to automatic clearance. Firms should ensure that their ASA contact details are up to date so that HMRC can reach them through the correct channel when the transition process begins. Firms that allow their contact information to lapse risk missing HMRC’s approach and inadvertently falling behind.
The Registration Process
The registration process is intended to be digital by default, with applications submitted through HMRC’s online platform. The application is made at firm level, reflecting the fact that this is a regulatory obligation imposed on the business rather than on individual fee earners.
As part of the process, firms will be required to identify those individuals who have a controlling or senior role in the provision of tax-related services — referred to in the legislation as “relevant individuals”. In a legal practice, this is likely to include partners, directors and senior managers involved in relevant workstreams, as well as employees who exercise control or significant influence over the firm’s tax-related activities. These individuals will be subject to checks as part of HMRC’s approval process.
The concept underpinning the regime is the introduction of minimum standards. To be registered, firms must demonstrate that they meet baseline requirements relating to matters such as tax compliance, anti-money laundering supervision and the absence of disqualifying conduct, including fraud or serious regulatory breaches. The structure of these requirements broadly reflects a “fit and proper” test and reflects a wider policy objective of improving standards across the tax advice market.
Registration will not be a one-off exercise. Firms will be expected to maintain their compliance with these standards on an ongoing basis and to provide updated information where required. HMRC will have the ability to suspend or remove firms from the register where conditions are no longer met.
There will, at this stage, be no charges made for an initial registration nor for staying on the register.
Consequences of Non-Registration
The introduction of the regime brings with it clear enforcement mechanisms. A firm that is required to register but fails to do so will not be permitted to interact with HMRC on behalf of clients. In practical terms, this means that the firm cannot submit SDLT returns, correspond with HMRC or otherwise progress matters that require engagement with the tax authority.
HMRC’s enforcement powers include the ability to issue compliance notices and stop notices. Where a firm continues to interact with HMRC without registering after a compliance notice has been issued, financial penalties apply: £5,000 for an initial breach, rising to £10,000 for repeat or more serious breaches. A £10,000 penalty also applies where a firm acts while subject to a suspension or prohibition from registration. Where HMRC considers a breach attributable to the actions of a senior manager, penalties may be levied against those individuals personally.
Additionally, if a firm’s registration is suspended for more than 30 days, it will be required to notify each of its clients of that suspension within 60 days — with a separate penalty of £5,000 per client for failure to do so. For solicitors’ firms, the consequences therefore extend beyond regulatory breach into client service risk. Transactions may be delayed or prevented from completing, and client relationships may be adversely affected.
This elevates registration from a compliance formality to a core operational requirement.
Practical Steps for Solicitors’ Firms
Although the timetable provides a structured rollout, firms should now be preparing for implementation. The first step is to identify whether and how the firm interacts with HMRC. In many cases, this exercise will reveal a wider scope of activity than initially anticipated.
Firms should then consider who within the organisation is responsible for those interactions and whether those individuals fall within the category of relevant persons for the purposes of registration. This links directly to governance and supervision arrangements, which may need to be formalised or documented more clearly.
It is also important to review existing HMRC access arrangements, including whether the firm operates an Agent Services Account and whether that account is properly configured and has up-to-date contact details. Alongside this, firms should ensure that their anti-money laundering supervision is in order and that there are no issues in relation to tax compliance that could affect eligibility for registration.
Responsibility for managing the registration process should be clearly allocated, typically to the COLP, COFA or another senior compliance function. As with other regulatory developments, early engagement and structured planning will reduce the risk of last-minute difficulties.
A Wider Regulatory Context
The introduction of mandatory tax adviser registration should be seen as part of a broader trend towards increased regulatory oversight of professional services. HMRC’s objective is not simply to create an administrative register, but to raise standards and improve accountability among those acting on behalf of taxpayers.<?p>
For solicitors’ firms, this sits alongside existing obligations under the SRA Standards and Regulations, the Money Laundering Regulations 2017 (as amended) and the wider focus on financial crime prevention. There is a clear convergence in regulatory expectations, particularly around governance, transparency and the role of senior management in overseeing compliance.
Firms that approach registration as part of their overall compliance framework, rather than as an isolated requirement, will be better placed to respond effectively.
We have produced a separate article dealing with tax adviser status from an AML perspective.
Conclusion
The publication of the timetable marks a shift from policy development to practical implementation. The key dates are now fixed, and the expectation is that firms will take active steps to ensure compliance within the relevant timeframe.
For most solicitors’ practices without an existing ASA, the critical date will be 18 August 2026, with registration opening from 18 May 2026 and a transitional period of three months available from that date. While this may appear some way off, the preparatory work required means that action should be taken now.
The firms that respond early — by understanding the scope of their activities, allocating responsibility, keeping HMRC contact details current and embedding the requirements into their compliance systems — will be best placed to manage both regulatory risk and client service continuity.
What Infolegal is Doing
To assist subscribers to the Infolegal InfoHub Infolegal has produced some additional terms and conditions which we will incorporate into our draft template Terms and Conditions in the Retainer Letters part of the Precedents and templates on the InfoHub. We will also indicate what these changes are. We have also produced a client explanation which can if required be added to client care letters. Finally, we will be producing a short training module addressing the changes.