Aggregation clause · Negotiation
How to negotiate PI aggregation clauses
Reviewed by Apex Insurance Brokers (FCA FRN 724952) · Published 15 July 2026
Aggregation clause language determines what happens when multiple claims arise from the same underlying cause. Getting it right can be the difference between one claim within limit and multiple claims exceeding it.
The three main aggregation approaches
- 'Series of related acts or omissions' — broad aggregation, more claims treated as one.
- 'Underlying cause' or 'unifying factor' — narrower aggregation, more claims kept separate.
- 'Single event' or 'single act' — narrowest aggregation, each claim usually separate.
- Wordings vary widely between insurers.
What favours the insured
- Narrower aggregation language (separate claims stay separate).
- Clear definition of what constitutes a 'related' claim.
- Explicit exclusion of 'series of similar' from aggregation.
- Aggregate limit high enough to absorb multiple related claims anyway.
- Reinstatement provisions to top up aggregate.
What favours the insurer
- Broader aggregation language (more claims into one).
- Ambiguous definitions leaving room for interpretation.
- Absence of reinstatement.
- Cap on 'per claim' basis limiting total exposure.
- Court-tested wordings the insurer has successfully argued.
Negotiation tactics
- Start with insurer's standard aggregation clause.
- Identify specific language that concerns you.
- Propose alternative wording informed by favourable case law (e.g., Lloyds TSB v Lloyds Bank Group).
- Request narrower aggregation for specific work types.
- Consider reinstatement as offset to broad aggregation.
- Document rationale for the wording chosen.
Sector considerations
- Solicitors: SRA MTC uses specific aggregation language — can be modified only within limits.
- Architects and engineers: BSA 2022 exposure adds urgency to narrow aggregation.
- IFAs: pension advice can generate multiple similar claims — aggregation matters.
- Accountants: audit engagements can have multiple stakeholders — aggregation nuanced.
- General consulting: often more room for narrower aggregation.
Frequently asked
Can I always negotiate aggregation?
For material placements with strong market position, yes. Smaller/simpler risks may have less flexibility.
What's the most claimant-friendly language?
'Series of related acts or omissions' aggregates more — insurer-friendly. 'Single event' or 'single act' aggregates less — insured-friendly.
Does aggregation matter if my limit is high?
Less so, but still material. Even high limits can be exceeded by aggregated claims.
Does the SRA MTC dictate aggregation for solicitors?
It sets minimums but doesn't fully dictate language. Some variation exists between qualifying insurers.
Can insurers change aggregation mid-policy?
Not unilaterally. Endorsements need mutual agreement.
How does case law inform negotiation?
Lloyds TSB v Lloyds Bank Group (2003) and other authorities give the vocabulary for negotiation.
Related
- Aggregation clauses by regulator
- PI claims aggregation case law UK
- Lloyds TSB v Lloyds Bank Group Insurance 2003
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