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"Same act or omission" — the narrowest aggregation trigger

If you want aggregation as a buyer, you want it broad: one excess across as many claims as possible, ideally without giving up too much limit-protection. If you want aggregation as an insurer, you want it broad too: one limit per cluster, regardless of how many separate acts the insured committed. Both sides therefore want broad aggregation rungs. The narrowest possible trigger — "same act or omission" — is wanted by neither.

This article explains what the trigger means, when it is operative, and why it is rarely used as a stand-alone aggregation wording in the modern UK PI market.

This article is Spoke 9 of the Apex hub on aggregation and series clauses in PI insurance.

Plain English explanation

"Same act or omission" aggregates claims that arise from precisely the same act or precisely the same omission. Not "similar" — same. So if a solicitor releases escrow money on five different transactions in five different letters, each release is its own omission. There may be five letters, five omissions, five claims — and no aggregation under this trigger. Only where literally one act or one omission has caused multiple claims (e.g. one letter wrongly addressed and delivered to twenty recipients) will this rung bite.

In practice, this kind of single-event-multi-claim scenario is rare in professional services. Most professional errors involve multiple acts or omissions over time, each in respect of a different file or client. So the "same act or omission" trigger fragments claims in almost every real-world case.

Insurers do not want a stand-alone narrow trigger because it leaves them exposed to multiple limits. Policyholders do not want it because it leaves them exposed to multiple excesses. The wording survives only as the narrowest rung in a hybrid ladder, where its function is to be the fallback when broader rungs do not apply.

How the trigger functions in a hybrid

In the SRA Minimum Terms (see Spoke 4), "one act or omission" is rung A — the narrowest. The other three rungs (related acts/omissions; same act/omission in related matters; similar acts/omissions in related matters) are broader. An insurer arguing aggregation uses the broadest rung first. The narrow rung is only ever decisive where the broader rungs fail and the narrow rung happens to apply because, on the unusual facts, one act or one omission really did cause multiple claims.

Examples where the narrow rung is decisive:

One letter, many recipients. A solicitor sends out a generic instruction letter to all participants in a scheme containing a single misstatement. All recipients act on the misstatement to their detriment. One letter = one act. Aggregation under the narrow rung.

One title certificate, many buyers. A solicitor certifies title on a block of flats. All buyers complete on the basis of the certificate. The certificate is defective. One certificate = one act. Aggregation under the narrow rung.

One audit report, many users. An auditor signs off accounts that turn out to be misstated. Investors, lenders and counterparties claim. One signature = one act. Aggregation under the narrow rung.

One press release, many recipients. A PR consultant drafts and issues a defamatory press release. Subjects of the release sue. One release = one act.

Outside these single-document, single-decision scenarios, the narrow rung rarely succeeds.

Why the modern market does not write the narrow rung as a standalone

Three reasons.

Adverse selection. A standalone narrow rung is uninsurable for insurers because it exposes them to multiple limits across any cluster involving multiple acts. The reinsurance market behind primary insurers will not support narrow standalone wording.

Commercial unviability for policyholders. A standalone narrow rung is also unattractive for policyholders because it fragments excesses across many small claims. A firm with 50 small claims and a £25,000 excess would pay £1.25 million in excesses with no aggregation.

Better hybrids exist. The hybrid wording produces a sensible balance: aggregation when the cluster is genuinely systemic; fragmentation when it is not. Both sides accept the hybrid as the workable equilibrium.

Worked example with numbers

Take a firm with £2 million primary, £25,000 excess. Cluster: 30 claims arising from a common methodological flaw across 30 unrelated client matters.

Hybrid wording (SRA-style): rung D (similar acts/omissions in related matters) likely fails because the matters are unrelated. Rung B (one series of related acts/omissions) likely succeeds because the omissions are related (common methodological flaw). Aggregation. One £25,000 excess. £2 million limit applied to aggregated cluster.

Standalone narrow wording ("same act or omission" only): the 30 omissions are not literally the same — they are 30 separate decisions on 30 separate files, even if methodologically identical. Aggregation fails. 30 excesses. 30 individual limits.

Net effect: in the hybrid policy, one excess and possible limit shortfall. In the standalone narrow policy, 30 excesses and no limit shortfall.

For most clusters the hybrid wording is the more sensible commercial proposition for both sides, which is why the market produces it.

When the narrow rung does still matter

Even in hybrid wordings, the narrow rung is occasionally decisive. Three scenarios where you might find yourself relying on it.

Single-document errors. As above, where one document is the operative act and is acted upon by many.

Single-decision errors. Where one professional decision affects many transactions (e.g. a single tax election that affects multiple tax years).

Single-recommendation errors. Where one professional recommendation is acted upon by multiple clients (e.g. a research note issued by an investment adviser to many clients simultaneously).

In each case, the broader rungs may also be available — but the narrow rung gives the cleanest argument because it identifies the single act and the immediate causal connection to the claims.

Sector implications

Solicitors. Narrow rung occasionally decisive in title certification, scheme documentation and bulk instruction letters. Rare otherwise.

Surveyors. Rare. Each valuation is its own act, even in panel work.

Architects. Rare. Design decisions are usually multiple over the course of a project.

Accountants/auditors. Rare except where a single audit opinion or single tax return is used by multiple parties.

IFAs. Occasionally — single research recommendation or model portfolio decision.

Engineers. Rare. Design decisions are usually multiple.

IT consultants. Occasionally — a single deployment decision affecting many systems.

What this means for your firm

Read your aggregation clause for the narrow rung. It is usually rung (a) or rung (i) of the ladder. Confirm that it is part of a hybrid, not standalone.

Identify your single-act exposures. Map any document, decision or recommendation that affects many parties simultaneously. These are the scenarios where the narrow rung is operative — and where aggregation under it usually helps you.

Notify single-act clusters as such. Where one act or one omission has caused multiple claims, notify accordingly. Identify the act, the document and the affected parties.

Do not assume narrow-rung aggregation gives you a wide limit. If you have an aggregated cluster of 50 single-act claims, you still face one £2 million limit. The narrow rung unifies the excess but not the limit (which it would do anyway under aggregation).

How the narrow rung interacts with broader rungs

In a hybrid wording the rungs interact as follows.

Each rung is independent. Aggregation succeeds if any rung applies.

Broader rungs prevail by inclusion. If rung D (broadest) applies, the narrow rung is redundant. The narrow rung only does work where broader rungs fail.

Narrow rung does not preclude broader rungs. A cluster that satisfies the narrow rung also typically satisfies one or more broader rungs. Insurers will plead broader rungs first.

Narrow rung helps the policyholder where broader rungs are contested. If the insurer is contesting aggregation (e.g. trying to multiply excesses on a small cluster), the policyholder can argue that the narrow rung applies even if the broader rungs are contested.

FAQs

Q1. Is there a standalone "same act or omission" wording in the UK market? Rarely. Most modern PI wordings include the narrow rung as part of a hybrid ladder.

Q2. Can I ask my insurer to remove the broader rungs and keep only the narrow rung? You can ask. You will not get it. The market is structured around hybrid wording.

Q3. When is the narrow rung most useful to me? When you have a single-document or single-decision error affecting many parties. The narrow rung lets you argue aggregation cleanly without needing to prove that the matters are related.

Q4. Can the narrow rung be defeated by the insurer arguing the cluster involves "similar" not "same" acts? The insurer would only argue that if they wanted fragmentation (e.g. to multiply excesses on a small cluster). On most clusters they want aggregation.

Q5. Does the narrow rung apply differently for omissions vs acts? No. The wording is "act or omission". Both are treated the same.

Q6. How do I argue that 50 letters were "one omission" rather than 50? You usually cannot. The case law treats separate documents as separate acts/omissions in the absence of unifying features (single template, single sending, single decision).

Q7. Is the narrow rung in the SRA Minimum Terms always rung (a)? Yes. SRA Minimum Terms clause 2.5(a) lists rungs in order from narrowest to broadest.

Q8. Do other professional bodies prescribe rung order? No. ARB, RICS, ICAEW, FCA — none prescribes aggregation language. The order in the policy reflects insurer drafting choices.

Q9. Does the narrow rung apply to defence costs? Yes — in the SRA wording, the aggregation regime applies to defence costs (clause 2.5(a)(iii)).

Q10. What is the most important practical takeaway? The narrow rung is rarely the decisive aggregation trigger but is a useful fallback. Make sure your wording is a hybrid that includes it, not just the broader rungs.

Same act or omission - the narrowest aggregator