What it means
Every liability policy has to answer one question before anything else: was this loss inside the period we agreed to cover? The trigger is the rule that answers it, by naming the event that pulls a particular policy year into play.
Get the trigger wrong and a business can hold a filing cabinet of policies and still find that none of them responds. An occurrence trigger looks at when the injury or damage took place.
If a faulty component was fitted in 2019 and the resulting fire happened in 2019, the 2019 policy responds even if the claim only arrives in 2026 and the insurer no longer writes that class of business. Cover is effectively locked in at the time of the event.
A claims-made trigger looks at when the claim is first made against the insured and notified to the insurer. Professional indemnity, directors and officers, and medical malpractice policies almost always work this way, and the practical consequence is stark: let the policy lapse and even claims arising from work done while you were insured may fall outside cover.
Because of that, claims-made policies come with two important features. A retroactive date sets the earliest work that can be covered, and run-off cover extends the ability to notify claims after the policy ends, which is essential when a professional firm winds up or a business is sold.
The trigger interacts with limits and deductibles, and this is where the arithmetic bites. Limits are usually per occurrence and in aggregate for the policy year, so if an old policy year with a low limit is the one triggered, the insured pays everything above that older, smaller amount even though today's policy carries a much higher limit.
Disputes about triggers are common in slowly developing losses. Where damage builds up over years, such as gradual water ingress or long-term exposure claims, courts and policies use different theories about which year or years are triggered, and multiple policy periods may end up sharing the cost.
In practice
Real-world examples.
Example
A roofing contractor is sued in 2026 over water damage traced to work completed in 2021. Its general liability policy is occurrence-based, so the 2021 policy year responds, with the limits and deductible that applied back then.
Example
An accountancy practice merges into a larger firm and cancels its own professional indemnity policy. Its partners buy six years of run-off cover, because otherwise a claim notified after cancellation would have no policy to trigger.
Example
A hospital group reviews its malpractice programme and finds the retroactive date on the claims-made policy is only three years old. It negotiates an earlier retroactive date so that older episodes of care remain capable of triggering cover.
Formula
Calculation
Insurer payment = Amount of the loss - Deductible or retention, capped at the per-occurrence limit of the triggered policy year.
A design consultancy settles a professional negligence claim for $1,400,000. The claim was notified in 2026, but the defective design work was done in 2019. The 2019 policy carried a $2,000,000 per-occurrence limit with a $250,000 deductible; the 2026 policy carries a $5,000,000 limit with a $100,000 deductible.
If the policy were occurrence-based, the 2019 year is triggered. Insurer payment = $1,400,000 - $250,000 = $1,150,000, which sits inside the $2,000,000 limit, and the consultancy bears the $250,000 deductible.
Because professional indemnity is written on a claims-made basis, the 2026 policy is the one triggered instead, provided the retroactive date is 2019 or earlier. Insurer payment = $1,400,000 - $100,000 = $1,300,000. Had the firm allowed cover to lapse in 2025 without buying run-off, no policy would respond at all and the full $1,400,000 would fall on the business.Case study
Seen in the real world.
Hollowbrook Design Partners is an invented architecture practice used here as an illustrative example. In 2019 it designed a drainage layout for a warehouse; in 2026 the owner sued after persistent flooding, seeking $1,400,000.
The practice assumed it was protected because it had held continuous professional indemnity insurance since 2015. That assumption survived scrutiny, but only just: when the firm restructured in 2023 it moved to a new insurer, and the new policy carried a retroactive date of 2023 rather than an unlimited one. Claims arising from work before 2023 would not have been covered.
Fortunately the broker had spotted the gap at the time and negotiated the retroactive date back to 2015 for a modest additional premium. The 2026 policy therefore responded, paying $1,300,000 after the $100,000 deductible. In this fictional case, a single date buried on the policy schedule was worth more than a decade of premium payments.
Watch out
Common mistakes.
- Assuming any policy in force at the time of the claim will respond. On an occurrence policy it is the year of the damage that counts, and on a claims-made policy the retroactive date can still exclude old work.
- Cancelling a claims-made policy when a business closes or is sold. Without run-off cover there is no live policy left for a future claim to trigger, and the exposure lands on the former owners.
- Only comparing premiums when switching insurers. A cheaper claims-made policy with a later retroactive date can quietly strip cover from years of past work.
Questions
People also ask.
What is a retroactive date?
The earliest date of work or conduct that a claims-made policy will cover; anything before it is excluded no matter when the claim is notified.
Which trigger is better for a business?
Neither is universally better; occurrence cover suits physical damage risks that surface late, while claims-made cover is standard for professional risks and needs careful management of the retroactive date and run-off.
Can more than one policy year be triggered by a single loss?
Yes, in gradual or continuing damage claims several years can be drawn in, and the policies then share the loss according to their wording and applicable law.
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