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HMRC tax adviser registration and SDLT: What law firms should be thinking about now

HMRC has confirmed that from May 2026, professionals who interact with HMRC on behalf of clients in relation to tax matters will need to register under a new mandatory tax adviser regime and meet “minimum standards”. Firms will have a transitional period of three months to register once the system opens.

23/03/2026 · 5 minute read

HMRC has confirmed that from May 2026, professionals who interact with HMRC on behalf of clients in relation to tax matters will need to register under a new mandatory tax adviser regime and meet “minimum standards”. Firms will have a transitional period of three months to register once the system opens.

The requirement is being introduced through the Finance Bill 2025–26.

For law firms, a key issue is that submitting stamp duty land tax (SDLT) returns when acting as a conveyancer will fall within the scope of the new requirements. Check if and when you need to register as a tax adviser with HMRC - GOV.UK. HMRC has confirmed this.

At first glance, this may look procedural. In practice, it raises some important risk and defensibility questions.

Why this matters

Under the Finance Act 2003, the purchaser remains the taxpayer and the solicitor acts as agent.

Most firms’ engagement letters reflect this and typically state:

“We will complete and submit the SDLT return on your behalf. We do not provide tax advice.”

If HMRC treats SDLT filing as “tax adviser interaction,” firms may find themselves in an uncomfortable position:

  • Required to register as a tax adviser in order to submit returns
  • While contractually stating that they are not providing tax advice

That tension does not automatically create liability, but it does alter how certain arguments may be viewed in the event of a claim.

Where we see potential exposure

1. Standard of care drift

If a firm is required to register as a tax adviser, a claimant may argue that this evidences tax advisory responsibility.

Courts look at substance rather than labels. If a firm is calculating SDLT, assessing higher-rate surcharge, or considering reliefs, it may be harder to characterise the role as purely administrative.

2. Scope-of-retainer challenges

Blanket statements that the firm does not advise on tax may become more difficult to rely upon if the work being undertaken is formally categorised as tax adviser activity.

The issue is not that disclaimers are ineffective, but that they need to align with the reality of the services provided.

3. Relief and surcharge claims

Historically, SDLT claims against solicitors have tended to arise from:

  • Higher-rate surcharge misapplication
  • Replacement of main residence errors
  • Mixed-use classification issues
  • Missed multiple dwellings relief
  • Late filing penalties

If the regulatory framing shifts, claimants may argue there was at least a duty to identify and flag relief considerations, even if not to provide full tax planning advice. That could increase the risk of claims against law firms.

Regulatory alignment

Under the Solicitors Regulation Authority Standards and Regulations, firms must provide services competently and ensure communications are not misleading.

If registration as a tax adviser becomes mandatory for SDLT filing, engagement letters and internal positioning should be reviewed to ensure consistency and transparency.

Practical risk mitigation steps

As May 2026 approaches, firms may wish to consider the following at the governance level.

1. Review engagement letter wording

Rather than broad statements that the firm does not provide tax advice, firms may consider more precise drafting, for example:

  • Clarifying that SDLT will be calculated and submitted based on transaction information
  • Confirming that broader tax planning advice is outside scope unless separately instructed
  • Stating that complex reliefs or structuring advice may require specialist tax input

This avoids overreach while maintaining defensible boundaries.

2. Consider when independent tax advice is appropriate

Firms may wish to consider whether certain SDLT matters should routinely involve independent specialist tax advice, particularly where:

  • The transaction value is high
  • Trust, corporate, or partnership structures are involved
  • Multiple dwellings relief or mixed-use classification is being considered
  • There is uncertainty over higher-rate surcharge application
  • The client has wider tax planning objectives connected to the transaction

This does not mean routine residential conveyancing requires external input. However, where SDLT analysis moves beyond straightforward calculation into judgement or relief strategy, independent tax advice may reduce both technical risk and the risk of claims made with the benefit of hindsight. Such claims are fuelled by a lack of clarity about the ambit of the firm’s role, and the client not being in an informed position as to whether specialist advice is needed.

Where referral is not made, firms should ensure that:

  • The scope of advice is clearly defined in writing
  • Any limitations are explained to the client
  • The client’s decision not to seek specialist advice (if recommended) is recorded

3. Escalation triggers and supervision

Firms may wish to formalise when SDLT matters should be referred internally or externally, particularly where complexity increases.

A broader observation

This is not simply a technical tax change. It reflects a wider trend of regulatory reclassification and increasing scrutiny of professional roles.

For firms that have historically treated SDLT as administrative, now is the appropriate time to revisit positioning, engagement wording, and internal controls — calmly and deliberately.

We are seeing some firms consider whether to outsource SDLT completion to specialist providers on a fully managed basis. For certain practice profiles, this may be an appropriate solution. However, outsourcing does not usually remove risk: it changes its shape.

Where firms adopt this model, careful due diligence will be important, including:

  • Clarity on the scope of responsibility
  • Contractual allocation of liability
  • Confirmation of adequate professional indemnity cover
  • Ongoing oversight and quality assurance of the provider 

Ultimately, whether SDLT is retained in-house or managed externally, the key issue is alignment: regulatory classification, engagement scope, competence, and supervision must sit comfortably together.

Firms that address this now are likely to be in a stronger position should scrutiny arise later.

Our people

John Kunzler

Risk and Error Management

  • United Kingdom

Victoria Prescott

Victoria Prescott

Risk and Error Management

  • United Kingdom