Professional negligence: why early legal advice matters (and why “wrong” isn’t always “negligent”)

Manisha Modasia, Associate

Commercial clients typically seek advice when a professional’s work has had a material impact on a transaction or project – an undervaluation affecting a sale, a flawed report influencing funding, or advice that drives an unexpected loss. It is common to assume that an incorrect outcome automatically equates to negligence. In practice, the legal analysis is more exacting.

The Court of Appeal decision in Bratt v Jones [2025] EWCA Civ 562 is a useful reminder of the distinction between a disappointing figure and actionable negligence. An independent expert valuer was appointed to value development land with planning permission to facilitate a buy-out between parties. The valuer assessed the site at £4.075 million; subsequent evidence suggested a market value in the region of £7 million to £8.6 million.

However stark the valuation gap, a claimant must still establish (i) breach of duty – i.e., that the professional’s approach fell below the standard of a reasonably competent practitioner – and (ii) causation and loss. A mistake in outcome is not, by itself, determinative.

Not every mistake is negligence

The courts distinguish between:

• A disappointing outcome, and
• A process that falls below the standard of a reasonably competent professional.

Professionals such as valuers, accountants, architects and solicitors are not judged against a standard of perfection. The court asks whether the professional acted with reasonable skill and care, applying the prevailing standards and guidance in their discipline at the time.

In many technical disciplines there is a permissible range of professional judgment. That is why a claim may fail even where the output appears “wrong” commercially: if the methodology, inputs and reasoning remain within an acceptable range, the legal threshold for negligence may not be met.

What should you look out for?

Where a professional’s work has driven a commercial decision, the key question is typically whether there were process failures (scope, inputs, method, reasoning, documentation) rather than whether the conclusion later proved unfavourable. Common indicators include:

• Scope or instructions not followed: the professional departs from agreed assumptions, brief, or terms of engagement without agreement.
• Key information omitted: material documents, constraints, market evidence, or risks are not considered (or are inaccurately recorded).
• Methodology not supportable: the approach is inconsistent with accepted practice, guidance, or peer standards in the relevant discipline.
• Unreasoned assumptions: critical assumptions are asserted without a clear evidential basis, sensitivity analysis, or explanation.
• Inadequate working papers: insufficient audit trail of inputs, calculations, and decision-making, making it difficult to verify the reasoning.

These issues go to breach of duty and evidential proof. They are also the areas where early document preservation, targeted requests and independent expert review can materially strengthen (or properly rule out) a claim.

Why you should speak to a solicitor early

Professional negligence disputes can be evidence heavy and strategically sensitive, particularly where there are live projects, lender requirements, audit considerations or parallel contractual claims. Early advice helps to preserve options, manage cost exposure and shape a proportionate dispute strategy:

• Limitation is unforgiving: you can lose the right to pursue a claim if proceedings are not issued within the relevant time limits.
• Evidence needs to be secured early: engagement letters, instructions, drafts, working papers and communications should be preserved and, where appropriate, requested promptly.
• Expert input shapes the case: independent expert evidence is often central to breach, causation and quantum; early scoping can avoid missteps and unnecessary cost.
• Protocol and settlement strategy matter: early analysis supports a well-judged pre-action approach, engagement with insurers, and sensible use of ADR (including mediation) where it best serves the commercial objectives.

Final thought

The lesson from Bratt v Jones is not that professionals are beyond challenge. It is that the viability of a claim depends on a structured assessment of breach, causation and loss – grounded in the engagement terms and the professional’s methodology – rather than the commercial disappointment of the outcome.

If you are considering next steps – whether as an in-house legal team, lender, developer or investor – early advice can help you protect the evidence, assess prospects and value, and decide whether to pursue a claim, negotiate a commercial resolution or take other protective steps.

If you would like a confidential discussion about a potential professional negligence issue, we can advise on early merits, evidence preservation, expert strategy and the most commercially appropriate route to resolution.