Anyone who interacts with HMRC on a client’s behalf must register with HMRC as a tax adviser from 18 May 2026 – including law firms, in-house tax teams, family offices and possibly barristers' chambers.
This new legal requirement, introduced by the Finance Act 2026, aims to ensure that those interacting with HMRC about someone else’s tax affairs, and getting paid for it, meet defined minimum standards and register for an agent services account.
Although “tax adviser” might not be a label many lawyers adopt, HMRC’s definition extends widely and captures a significant proportion of legal work involving HMRC-related submissions.
Why do law firms need to register with HMRC?
The new registration regime forms part of HMRC’s wider programme to improve standards within the tax advice market and reduce the use of unregulated or non‑compliant intermediaries.
For law firms, this represents a notable shift. Legal practices that do not offer tax advisory services in the traditional sense may nevertheless fall within scope by virtue of routine interactions with HMRC—particularly in conveyancing, probate, corporate, trust and estate work.
Who must register?
HMRC’s definition of a “tax adviser” is intentionally broad, and any individual or firm that interacts with HMRC regarding a client’s tax position will need to register.
This is expected to include:
Conveyancers and property lawyers Those submitting SDLT returns will be required to register. HMRC has indicated that SDLT submissions constitute a form of tax engagement for the purposes of this regime.
Probate and private client practitioners Anyone submitting inheritance tax forms or communicating with HMRC regarding a deceased person’s tax affairs will be in scope.
Corporate and commercial lawyers Where lawyers submit notifications, seek tax clearances, or otherwise liaise with HMRC, they will need to be registered.
Trusts and estates specialists Practitioners interacting with HMRC on trust registrations or estate tax matters are included.
Litigation and dispute resolution lawyers Those representing clients in a dispute with HMRC will also fall within scope—even if they do not prepare returns.
Firms with existing agent services accounts will migrate into the new system, and HMRC will contact those it requires more information from.
In short, if your firm communicates with HMRC on a client’s behalf and that communication influences a tax position, registration will likely be required.
When to register
HMRC intends to launch the new online system from 18 May 2026, and there are multiple registration deadlines, depending on the services you provide:
18th May 2026 – three-month registration period opens for those who do not have an existing agent services account, self-assessment or corporation tax account
18th August 2026 – registration for those who already have a self-assessment or corporation tax account
18th November 2026 - registration for those who only provide third-party payroll services
All legal entities providing tax-related services—traditional firms, ABSs, sole practices, and externally facing in-house teams—must register. Individual employees will not need to register, however HMRC will require details of “relevant individuals” responsible for oversight of tax-related work, such as department heads, supervising partners, or compliance officers.
Firms will need to self-certify compliance with HMRC’s Standards for Agents, expected to include:
acting lawfully and with integrity
maintaining professional competence
supervising staff effectively
managing tax risks
maintaining adequate systems, processes and records
Registration will not be a one‑time event. Firms must keep information up to date and cooperate with HMRC monitoring.
Practical implications for law firms
Dual regulation with legal regulators
The new regime adds HMRC oversight alongside existing requirements from the SRA and other regulators. While SRA regulation focuses on client care and ethics, HMRC’s regime is targeted at accuracy of tax‑related submissions, adviser behaviour in dealings with HMRC and the prevention of tax-related misconduct.
Increased compliance burden
Firms may need to review workflows, supervision arrangements, tax competence, systems, and engagement letters.
Risk of exclusion
HMRC will have powers to restrict or prevent individuals or firms from acting if they fail to meet standards. For high‑volume SDLT practices, this would be operationally significant.
Opportunities
Strong compliance frameworks may enhance client trust, reduce risk, and differentiate firms from lower‑quality providers.
Preparing for HMRC registration
Firms must first confirm whether they are in the scope of this requirement (most are). We recommend that firms then begin to:
Map all workflows involving HMRC submissions.
Identify relevant individuals who supervise or take responsibility for tax-related work.
Review competence and training across SDLT, probate, trusts, and corporate teams.
Update engagement letters and terms of business where references to tax-related work are required.
Failing to register risks reputational damage, inability to act for clients in interactions with HMRC, increased scrutiny from the SRA and possible civil or criminal consequences in cases of serious misconduct.
Next steps for law firms
As detailed operational guidance is yet to be released, law firms are encouraged to monitor HMRC announcements, and sector‑specific commentary from the SRA, the Law Society, and representative bodies such as the Council for Licensed Conveyancers.
Firms should ensure that this remains an active agenda item, particularly as final guidance is issued and the practical implications for individual practice areas become clearer.
If you would like further advice and support, please get in touch. Call 0808 144 5575 or email help@armstrongwatson.co.uk.
