From 18 May 2026, solicitors who submit SDLT returns, IHT forms, probate tax documents, and a wide range of other HMRC-facing work on behalf of clients will need to register with HMRC as ‘tax advisers’. If you have been receiving some alarming emails about this, take a breath. Here is what is actually happening – and what you sensibly need to do.

The short version: this is a registration requirement, not a new professional qualification or an assessment of the quality of your advice. Registration is free, will be done online, and firms have a three-month transition window after 18 May to complete it. There is plenty of time to do this calmly and correctly.

The headline is this: if your firm submits SDLT returns, inheritance tax forms, probate-related tax documents, or any other information to HMRC on behalf of clients – and is paid for doing so – you will need to register as a ‘tax adviser’ under a new mandatory registration scheme that opens on 18 May 2026. This has prompted considerable consternation in the legal profession, largely because most solicitors doing this work would never describe themselves as tax advisers in the conventional sense. The Law Society lobbied hard for an exemption. It was not granted. Today (27 April) they issued guidance to support affected law firms who have concerns about the requirements.  That guidance can be found here. 

But the requirement itself, while genuinely new, is manageable. Let’s look at it properly.

What has changed, and why

HMRC has long wanted greater visibility over who interacts with it on behalf of taxpayers. Its concern has been the unregulated end of the tax advice market i.e. individuals and organisations that provide tax services with no professional oversight, no minimum standards, and no accountability when things go wrong. The mandatory registration scheme, introduced through the Finance Bill 2025–26, is its solution: a single, digital register of everyone who interacts with HMRC in a tax-related capacity on behalf of clients, for payment.

The government has invested £36 million in modernising HMRC’s registration infrastructure to support this, replacing a fragmented, often paper-based system with a single online route via the Agent Services Account (ASA) platform.

What HMRC was not primarily thinking about when it designed this scheme was the conveyancer submitting a routine SDLT return as part of a house purchase, or the private client solicitor filing an IHT400 as part of a probate administration. These are people who have always been subject to professional regulation, supervised for AML purposes, and held to the highest ethical standards in the profession. The Law Society, the Council for Licensed Conveyancers, and the Conveyancing Association all made this argument forcefully during the consultation process. They were heard, but not exempted.

So here we are. The legislation is passed. The register opens in May. And the profession needs to get on with it.

Are you actually in scope?

The definition of ‘tax adviser’ in the legislation is deliberately broad. It captures any firm or individual that, as part of its business and for payment, assists others with their tax affairs. Specifically, this includes:

• Submitting or helping submit tax returns, claims or elections to HMRC on a client’s behalf
• Communicating with HMRC on a client’s tax matters, by phone, post, email, or through any HMRC digital service
• Sending information or documents to HMRC that relate to a client’s tax position

If your firm does any of these things in the course of its work, it is almost certainly in scope  regardless of whether you have ever described yourself as a tax adviser, and regardless of whether tax work is your main activity or an incidental part of a wider legal service.

In practice, this is likely to affect the following practice areas in most firms:

• Conveyancing: SDLT returns are the obvious and most widespread example. Filing an SDLT1 form on behalf of a buyer is, under this legislation, a tax adviser function. This alone brings the majority of conveyancing practices within scope.
• Private client and probate: Inheritance tax forms (IHT400 and associated schedules), trust tax compliance, estate administration involving HMRC correspondence, and CGT reporting on property disposals all fall within the definition.
• Family: Work involving CGT on family home disposals, trust taxation in financial remedy proceedings, and maintenance arrangements with tax implications may bring family practitioners within scope.
• Corporate and commercial: Corporate transactions involving tax filings, stamp duty on share transfers, and HMRC correspondence in M&A contexts are within scope.
• Dispute resolution: Contentious tax work and representation in HMRC enquiries or appeals (other than appeals to a court or tribunal, which are expressly excluded) may also be caught.

If you are uncertain whether a specific area of your firm’s work brings it within scope, the Law Society’s guidance and the HMRC guidance published on 17 February 2026 are the right places to start. The Law Society has been vocal about the ambiguities in the regime and is actively seeking clarifications from HMRC on a number of points, particularly around the definition of ‘relevant individuals’ within larger practices.

Law firms are far from alone in this

It is worth stepping back for a moment to note that the legal profession is not being singled out here. The mandatory registration requirement is a cross-sector measure that will affect a very wide range of businesses – and many of them are equally surprised to find themselves within scope.

Accountancy firms and tax practices are the most obvious group, and many will already hold Agent Services Accounts through their existing tax agent work. But the breadth of the definition catches many others:

• Payroll providers: (i.e. chasing PAYE codes or making HMRC enquiries) fall within scope, with a slightly later registration deadline of 18 November 2026.
• HR and employment consultancies: i.e. communicating with HMRC about a client’s employee tax affairs as a paid service could be caught, depending on the nature of those interactions.
• Financial advisers and wealth managers: This is a particularly interesting area. The original draft of the legislation cast such a wide net that it would have pulled in fund managers, regulated investment firms, and other financial services businesses simply through routine administrative HMRC interactions. The government recognised this was unintended and, in March 2026, deferred the registration requirement for financial services businesses to 31 March 2027 while it works with the sector to refine the scope. This is a helpful data point for law firms: it shows that HMRC is willing to adapt where a broad definition produces disproportionate results, and that the profession’s ongoing engagement – through the Law Society and others – may yet produce further clarifications.
• Corporate service providers and company secretarial firms: Businesses that interact with HMRC as part of company administration, tax filings, or statutory reporting on behalf of client companies will generally be in scope.
• Specialist tax boutiques and independent tax consultants: These are the firms the registration regime was primarily designed to address — the unregulated end of the tax advice market. For them, the registration conditions around AML supervision and tax compliance history are the most substantive hurdle.

What registration actually involves

This is where many firms will find the reality considerably less alarming than some of the communications circulating suggest.

Registration takes place at the level of the legal entity – the firm itself, not individual fee-earners. This is an important and welcome clarification. However, the registration process does require the firm to identify and provide information about ‘relevant individuals’ – those who manage or exercise significant control or influence over the firm’s tax-related work. In practice, for most firms, this will include partners, LLP members, or directors. There are minimum number requirements that vary by firm size.

The minimum conditions that firms and relevant individuals must meet are straightforward:

• Compliance with tax obligations – the firm and relevant individuals must not have outstanding, unresolved tax non-compliance
• No prior sanctions – no existing anti-avoidance measures, prior penalties under the new regime, or director disqualifications
• AML supervision – the firm must be under appropriate AML supervision. For SRA-regulated firms, this is already the case.
• No registration prohibitions that prevent participation in the scheme

For the vast majority of well-run, SRA-regulated law firms, these conditions will already be met as a matter of course. The AML supervision condition in particular is satisfied automatically by virtue of SRA regulation, which is one of the reasons the Law Society argued – with some justice – that an exemption or fast-track for SRA-regulated firms would have been appropriate. That argument was not successful, but the underlying point holds: firms that are already properly regulated and compliant should find the registration process relatively straightforward.

Thankfully, there are no registration fees. The process is entirely online. HMRC has confirmed that further guidance will be published before 18 May, and that firms which already hold an Agent Services Account will be contacted through that account rather than needing to register from scratch.

The three-month transition window

The registration window opens on 18 May 2026, but firms have three months from their required registration date to complete the process – and during that period they can continue to interact with HMRC on behalf of clients as normal. This is a sensible transitional arrangement that gives the profession time to work through the process without disrupting live transactions.

The phased timeline looks like this:

• 18 May 2026: Registration portal opens. Most law firms – those without an existing Agent Services Account, Self Assessment online account, or Corporation Tax online account – will need to register from this date (but have three months to do so).
• 18 August 2026: Firms that already have a Self Assessment or Corporation Tax account but no Agent Services Account must register by this date.
• 18 November 2026: Firms that provide only third-party payroll services register by this date.

Firms can register voluntarily before their required date from 18 May onwards. There is no penalty for registering early.

The ‘tax adviser’ label: should you be worried about what it implies?

This is a genuinely reasonable question, and one that the profession has been asking loudly. If your firm is now formally registered as a ‘tax adviser’ with HMRC, does that change the scope of your duties to clients? Could it give rise to negligence claims from clients who assumed you were providing comprehensive tax advice when you were merely submitting a form?

The analysis from practitioners who have examined this carefully is reassuring. The registration label describes the function – interacting with HMRC on behalf of clients – not the scope of the retainer. If your engagement letter already makes clear that you are submitting an SDLT return on the basis of information provided by the client, and that specialist tax advice on complex matters is outside scope, the registration label does not override that. The retainer governs the extent of the duty, not the HMRC category.

That said, this is a good moment to review engagement letter wording. Some straightforward additions are sensible practice going forward:

• A brief explanation that the firm is required to hold HMRC registration in order to submit tax-related documents on the client’s behalf, and what ‘tax adviser’ means in this context
• Clarification that SDLT, IHT or other submissions are made on the basis of information provided by the client and that the scope of the retainer does not extend to comprehensive tax planning advice unless separately instructed
• Where relevant, a recommendation that the client seeks independent specialist tax advice on complex matters such as SDLT reliefs, IHT mitigation strategies, or CGT planning

None of this represents a fundamental change to your client care obligations. It is simply good housekeeping – making the scope of the service clear, as you should be doing in any event.

What happens if you don’t register?

We know that some firms have received some fairly alarming marketing communications about this particular change, with messaging designed to generate a sense of panic rather than clarity. What you need is a clear-eyed understanding of what is actually happening, who is affected, and what the straightforward steps to compliance look like.

We mention this not to alarm, but because it’s important to understand the stakes. If a firm that is required to register fails to do so and continues to interact with HMRC on behalf of clients, HMRC can:

• Issue a formal notice requiring the firm to stop interacting with HMRC on behalf of clients
• Temporarily or permanently ban the firm from registering
• Impose a financial penalty of £5,000, rising to £10,000 for more serious or repeated breaches, against the firm and/or relevant individuals
• Require a suspended firm to notify all its clients of the suspension if it exceeds 30 days

For conveyancing practices in particular, the practical consequence of being unable to file SDLT returns is severe. Without a registered SDLT submission, there is no SDLT5 certificate. Without the certificate, Land Registry registration cannot proceed. Transactions stall. Clients are harmed. Claims follow.

This is why, while the registration process itself is straightforward, it is not something to leave until the last minute. The three-month window is generous but not infinite.

The AML angle: one more reason it’s already half-done

There is a point worth making specifically for the compliance professionals reading this. HMRC’s minimum registration conditions include confirmation that the firm is under AML supervision. For SRA-regulated firms, that condition is automatically satisfied – you are already supervised.

But there is a subtler connection too. The registration conditions will be checked on an ongoing basis, with annual assurances required. AML compliance status is part of what HMRC will be monitoring as part of maintaining registration. This does not mean HMRC becomes your AML supervisor. The SRA retains that role (for now!). But it does mean that an AML compliance failure could, in principle, affect HMRC registration status.

This reinforces a point we have made elsewhere: AML compliance is not just an SRA matter. As the FCA takes over AML supervision, as HMRC introduces registration conditions that reference AML status, and as the CQS audit programme intensifies, the interconnection between these regulatory frameworks is becoming tighter. Good AML compliance is foundational to a firm’s ability to operate across multiple dimensions, not just its regulatory standing with the SRA.

Quick checklist: what to do before 18 May

1. 1. Confirm whether your firm interacts with HMRC on behalf of paying clients (the answer is almost certainly yes if you do conveyancing, private client, probate, corporate or family work involving tax)

2. Check whether your firm already holds an Agent Services Account — if so, HMRC will contact you; you do not need to re-register

3. If not, prepare to register from 18 May via the new online portal

4. Identify who in your firm qualifies as a ‘relevant individual’ – partners/LLP members/directors and senior employees with control or significant influence over tax-related work

5. Review your engagement letter wording to include brief, clear language about the scope of tax-related services

6. Make a governance decision about which HMRC-facing services your firm will continue to offer, and document it

7. Note the dates in your risk register and assign a named person to manage the registration process

Our overall take

This is a genuine regulatory change that will affect most law firms, and it deserves proper attention. But it does not deserve panic. The registration process is free, online, and transitional. The minimum conditions are ones that well-run SRA-regulated firms should already meet. The scope of your legal duties is not altered by the label HMRC assigns to your registration.

What it does require is a clear-headed assessment of which parts of your work bring you within scope, a plan for getting registered in good time, and some tidying up of engagement letter wording. None of that is beyond any competent compliance function, and none of it requires expensive external assistance to accomplish.

The firms that will run into trouble are not those that take a calm, organised approach to this over the coming weeks. They are the firms that ignore it until June and then discover they cannot file an SDLT return on a live transaction.

Start now. Keep it in proportion. And if you have specific questions about how the regime applies to your firm’s particular practice profile, the Law Society’s guidance and HMRC’s own materials are the right first port of call.