Costs lawyers professional indemnity insurance — the complete UK guide 2026

Professional indemnity insurance for costs lawyers covers the legal liability arising when costs work — budgeting, bill preparation, detailed assessment advocacy, costs strategy advice — causes a client (typically a solicitor firm) to lose costs recovery. This guide sets out the CLSB and SRA regulatory frameworks, the post-Jackson costs environment, and how to structure cover.

Costs lawyers regulate under the Costs Lawyers Standards Board (CLSB). CLSB minimum PII is £100k per claim. Most costs lawyers work in SRA-authorised firms so PI typically runs under the SRA MTC with costs-work extension. Post-Jackson costs regime (LASPO 2012) generates distinct claim patterns around budgeting, proportionality and detailed assessment.

The regulatory framework for costs lawyers

Costs lawyers regulate under the Costs Lawyers Standards Board (CLSB), an independent body established under the Legal Services Act 2007. The Association of Costs Lawyers (ACL) is the professional body.

CLSB and CPR Part 46 context

The CLSB Code of Conduct applies to regulated costs lawyers. CPR (Civil Procedure Rules) Part 46 governs costs assessment and provides the litigation framework within which costs lawyers work. Practice failures often crystallise at detailed assessment hearings.

PII adequacy under CLSB rules

The CLSB requires PII of at least £100k per claim as absolute minimum. Individual firm adequacy standards typically much higher — £500k floor common; £1m+ standard for material caseload.

Overlap with SRA regulation

Where a costs lawyer works in a SRA-authorised firm, PI typically runs under the SRA MTC covering costs work as part of firm activity. Independent costs consultancies need standalone PI cover.

Post-Jackson costs environment

The Jackson reforms (LASPO 2012) fundamentally reshaped costs practice. Costs budgeting under CPR Part 3.13, proportionality under CPR 44.3, and detailed assessment procedures under CPR 47 all generate distinct claim patterns.

What costs lawyers PI insurance actually covers

Costs-lawyers PI covers legal liability from a breach of professional duty in costs work.

• Under-set costs budget causing client to face costs cap.
• Missed detailed-assessment deadlines.
• Errors in bill of costs preparation.
• Advice on costs strategy subsequently found deficient.
• Advocacy errors at detailed assessment hearings.
• Defence costs for civil claims and CLSB disciplinary matters.

What claims typically look like

Claims patterns for costs lawyers tend to cluster around a small number of scenarios. Each has its own defence and reserve profile. The list below is illustrative of the types insurers actively track for pricing and appetite decisions.

Choosing the right cover limit

Cover limit selection is the single biggest structural decision in a PI placement. Under-cover means an aggregation event exhausts limit before defence costs are paid. Over-cover wastes premium on a limit no realistic claim would reach. The bands below reflect how experienced professional insurers think about limit selection for costs lawyers.

Run-off cover and long-tail exposure

Costs-lawyer claims typically arise when a costs assessment fails at detailed assessment, or when a costs budget was under-set. Claim tails commonly match the underlying litigation timeline — six years or more from cost incurred.

Standard practice: six-year run-off minimum; extended run-off where costs work related to deed-executed litigation. Run-off premium typically 250-350% of final annual.

How insurers rate this class

Insurers segment costs lawyers by practice type.

• Solicitor-firm costs department — PI usually SRA MTC covering costs work as part of firm practice.
• Independent costs consultancy — standalone PI needed. Rate 1.5% to 3%.
• Costs draftspersons operating on freelance basis — individual PI cover.
• Costs specialists doing detailed assessment advocacy — wider scope; specialist market.

Deep-dive sub-topics

The topics below explore the technical decisions that most affect costs lawyers PI outcomes. Each links out to the standalone deep-dive page.

SRA MTC vs standalone costs PI

Costs lawyers in SRA firms usually covered by MTC. Independent consultancies need standalone. Wording must specify costs-work activities.

Post-Jackson costs regime

The 2013 costs reforms created new claim patterns around budgeting, proportionality and detailed assessment. Cover-limit selection should reflect the practice's exposure to budgeted cases.

Frequently asked

Related reading

• Solicitors sector pillar
• SRA MTC minimum terms explained