Aggregation clauses by regulator — UK 2026 side-by-side
Aggregation is the mechanism by which multiple claims arising from a common cause are treated as one for policy-limit purposes. Different UK professional-body PI regimes handle aggregation differently. This page sets out how the major regulators frame it, and where the differences matter for practical placement decisions.
Why regulatory frame matters
The regulator's minimum-terms document sets the outer boundary of what aggregation wording an insurer must offer. Where the MTC (or equivalent) mandates specific aggregation language, the insurer cannot use a broader aggregation trigger. Where the MTC is silent, the insurer's standard wording controls.
So knowing the regulator's aggregation position is knowing what floor of protection the profession enjoys. Above the floor, market-standard wording is where the negotiation happens.
SRA MTC — solicitors
The wording
The SRA MTC (2013 revised) uses the language ‘the same or a related series of acts, errors or omissions’. This is broad aggregation language.
Case law
AIG v Woodman [2017] Supreme Court decision confirmed that ‘related’ requires a real and material connection between the acts, not merely coincident timing or shared subject-matter.
Practical effect
Conveyancing series claims (multiple flat owners in the same block affected by one common error) aggregate to a single MTC limit. Firm-level exposure per event is thus £2m/£3m — the MTC minimum — unless the firm carries top-up above the MTC.
ARB — architects
The wording
ARB does not prescribe aggregation wording. Standard-market architects' PI uses ‘each and every claim’ language for many wordings, meaning fewer aggregation triggers. But wordings vary widely.
Practical effect
Firms doing residential-block or multi-unit-development work should review aggregation carefully. A single design defect across multiple homeowners can trigger aggregation depending on the specific wording.
BSA 2022 s.135 overlay
The 30-year tail on higher-risk-building work materially raises the stakes. Firms with BSA-touching residential work face aggregation risk over a much longer horizon than the standard six-year architect tail.
RICS — surveyors
The wording
RICS PII Requirements prescribe minimum standards. Aggregation wording is typically ‘same originating cause’ framing — broad but not as broad as SRA MTC series language.
Practical effect
Valuation work is the highest-volume claim category. Where the surveyor has used a common valuation methodology across multiple properties, aggregation triggers are common. Sub-limits per property and per single valuer are typical.
Insurance Act 2015 fair-presentation overlay
Fair-presentation questions at renewal about aggregation-relevant activity (large developments, repeat clients, valuation-in-bulk work) matter.
ICAEW — accountants
The wording
ICAEW Bye-law 61 prescribes the 2.5x fee income formula for minimum cover but does not mandate specific aggregation language. Standard-market wordings use ‘same act, error or omission’ language commonly.
Practical effect
R&D tax credit advisers face the sharpest aggregation risk post-2022 — a shared methodology across multiple clients challenged by HMRC creates a textbook aggregation event. Wording review essential.
FCA MIPRU 3 — insurance brokers
The wording
FCA MIPRU 3.2.7R prescribes minimum cover in euro terms. Aggregation is not directly mandated by MIPRU; the wording follows the market-standard broker PII language.
Practical effect
Placement error across multiple clients (e.g. wrong policy structure applied consistently) creates aggregation exposure. Wholesale brokers with delegated authority face aggregation across the entire binder book.
IPReg — trademark and patent attorneys
The wording
IPReg PII Rules prescribe per-claim and aggregate minimums scaled to fee income. Standard wordings use ‘same or connected series of acts’ language.
Practical effect
Filing-methodology errors affecting multiple clients create aggregation triggers. Firms with high-volume repeat clients face concentrated aggregation risk.
Side-by-side summary table
RICS (surveyors): Typically ‘same originating cause’ — moderate.
ARB (architects): Not prescribed; per-claim wording common; BSA 2022 stretches tail.
ICAEW (accountants): 2.5x fee income minimum; ‘same act’ typical.
FCA MIPRU (brokers): Euro-denominated minimum; wording market-standard.
IPReg (attorneys): Fee-income scaled; ‘same or connected series’ typical.
Practical testing checklist
- Know your regulator's baseline.
- Read the specific policy wording word by word.
- Test against your practice profile: shared methodologies, repeat clients, common product lines.
- Test worst-case scenarios in insurer discussions at renewal.
- Consider excess layers with independent aggregation treatment where primary is aggregated.