Trigger clause

Category: Policy structure · Reviewed by the Apex broking team · Last reviewed 2026-08-21 · ~3 min read

Definition

Insurance responds to events located in time. The trigger is the connecting factor the policy uses to decide whether a given loss belongs to a given period of insurance. It is distinct from causation: a policy responds only if the loss is both within the trigger and proximately caused by an insured peril, a question dealt with under proximate cause.

The three main bases

Losses-occurring / occurrence

The policy responds if the injury, damage or occurrence happens during the period of insurance, whenever the claim is eventually made. UK employers’ liability and public liability are conventionally written on this basis, which is why an employer may face a claim decades later on a policy long since expired. The advantage is that once a year has been covered, that year stays covered; the difficulty is finding and proving the historic policy.

Claims-made

The policy responds if the claim is first made against the insured during the period of insurance (and, in claims-made-and-reported wordings, is also reported within it or within a specified extension). Professional indemnity, directors’ and officers’, cyber and most financial lines are written this way. The current year’s policy deals with today’s claims about past work, subject to any retroactive date. The short entry on claim made deals with this trigger on its own.

Discovery / losses-discovered

The policy responds if the loss is discovered during the period, regardless of when the underlying act occurred. Crime and fidelity covers commonly use this basis, because employee dishonesty is typically concealed for a long time before it comes to light.

Triggers in long-tail liability: the EL trigger litigation

Where injury develops slowly, identifying the year the trigger operates can be genuinely difficult. In the employers’ liability trigger litigation, Durham v BAI (Run Off) Ltd [2012] UKSC 14, the Supreme Court considered mesothelioma claims under policies variously covering disease “contracted” and injury “sustained” during the period. It held that, on the proper construction of these employers’ liability wordings, the relevant policy was the one on risk at the time of the wrongful exposure to asbestos, rather than at the much later date the disease manifested. The decision matters far beyond asbestos: it shows that trigger wording is construed against the commercial purpose of the cover, which in employers’ liability is to insure the employer’s liability for exposure during the years of employment.

Gaps and overlaps when the basis changes

The dangerous moment is a change of basis or a change of insurer. Two patterns recur.

• Occurrence to claims-made. Work done in the occurrence years is covered by those policies, but a claims-made policy taken out afterwards may exclude claims arising from acts before its retroactive date, leaving the insured relying on the ability to trace old policies.
• Claims-made year to claims-made year. The new insurer will exclude claims and circumstances known before inception; the old insurer will only pick them up if they were notified during its period. A matter known but not notified before expiry can therefore fall between the two. This is the single most common coverage gap in professional lines and is avoided by disciplined notification of claim.

Ceasing to trade

Under a losses-occurring policy, cover for past years survives without further action. Under a claims-made policy it does not: once the policy is not renewed there is nothing on risk to receive a future claim, which is why a business winding down buys run-off cover. Where a company is dissolved or becomes insolvent, a third party with a claim against it may proceed directly against its insurer under the Third Parties (Rights against Insurers) Act 2010, which came into force on 1 August 2016 and allows the claimant to bring proceedings against the insurer and to obtain information about the policy.

Why it matters

Limits, excesses, exclusions and insurers all differ from year to year, so the trigger decides not only whether there is cover but how much and on what terms. When reviewing a programme, the trigger is worth identifying for every section before anything else: it determines what questions to ask about history, notification and run-off. The precise moment a claims-made policy is engaged depends on the date of notification.

Frequently asked questions

What is the difference between an occurrence policy and a claims-made policy?

An occurrence or losses-occurring policy responds to injury or damage happening in the period, whenever the claim arrives. A claims-made policy responds to claims first made against the insured during the period, subject to any retroactive date.

Which basis do UK employers' liability and public liability policies use?

They are conventionally written on a losses-occurring basis, so the policy on risk when the injury or damage occurred is the one that responds, even many years later.

What happens to claims-made cover if I stop trading?

Nothing is left on risk to receive future claims once the policy lapses, so run-off cover is normally bought to keep a claims-made policy available for claims arising from past work.

Can a claim fall between two claims-made policies?

Yes. If a circumstance was known before renewal but not notified to the expiring insurer, the new insurer will usually exclude it as a known circumstance and the old insurer will say it was never notified.

Related entries

• Claim made
• Notification of claim
• Date of notification
• Proximate cause
• Employers' liability insurance

This entry is part of the Apex Insurance Wiki. Last reviewed 2026-08-21. Next review: 2027-02-21. It is general reference information about UK insurance law and market practice, not regulated advice on a specific policy.

Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This page is general information, not advice on a specific policy.