8.3 Occurrence vs. Claims-Made Triggers

The Two Coverage Triggers

A coverage trigger is the event that activates a liability policy. The Insurance Services Office (ISO) writes the Commercial General Liability in two trigger versions — the CGL Occurrence form (CG 00 01) and the CGL Claims-Made form (CG 00 02). Knowing which event turns the policy on, and how the dates line up, is one of the most heavily tested concepts in the casualty exam.

Occurrence Trigger — "When Did It Happen?"

Under an occurrence policy, what matters is when the injury or damage occurred, not when the lawsuit arrives. A 2020 occurrence-form policy covers a 2020 injury even if the suit is filed in 2026 (subject to the statute of limitations).

This is ideal for long-tail exposures only up to a point — it creates the problem of stacking and old policies being reopened years later. The insuring agreement requires the BI/PD to occur during the policy period and to result from an "occurrence" defined as an accident, including continuous or repeated exposure to substantially the same harmful conditions.

Claims-Made Trigger — "When Was the Claim Filed?"

A claims-made policy responds only if the claim is first made during the policy period AND the injury occurred on or after the retroactive (retro) date. Two dates must both line up:

1. Retroactive date — the earliest date of injury the policy will cover. Injury before this date is never covered, no matter when the claim arrives. Advancing or deleting the retro date is a serious coverage cutback.
2. Claim date — the claim must be reported during the active policy period or an extended reporting period.

Trap: If the retro date is moved forward at renewal, prior acts lose coverage. Watch exam questions where a loss occurred just before a newly advanced retro date — the answer is no coverage.

Extended Reporting Periods (Tail Coverage)

Because a claims-made policy stops covering claims after it ends, the ISO form provides Extended Reporting Periods (ERPs) — "tail" coverage — to report claims after expiration for injuries that occurred during the policy term:

• Basic (Automatic) ERP — provided at no charge. A 60-day window to report claims for occurrences known to the insured, plus a 5-year "mini-tail" for occurrences reported to the insurer within 60 days.
• Supplemental ERP — must be purchased (usually within 60 days of expiration), for an additional premium capped at a percentage of the expiring premium, providing unlimited time to report.

Worked Date Scenario

A claims-made CGL runs 1/1/2026–12/31/2026 with a retro date of 1/1/2023.

Compare an occurrence policy for 2026: a 6/1/2026 injury is covered no matter when the claim is filed.

Why the Industry Created Claims-Made Forms

The ISO introduced the claims-made CGL in 1986 to control long-tail exposures — claims (asbestos, pollution, latent injury) that surface years or decades after the harmful exposure. Under occurrence forms, insurers could be forced to pay decades-old policy years they had long since forgotten, making reserving and pricing nearly impossible. Claims-made forms close the tail by tying coverage to the report date, letting insurers reserve more accurately and reprice each year.

The Five Claims-Made Maturity Steps

A claims-made program typically matures over years. As the retro date stays fixed and the policy renews, premiums rise from a first-year (immature) discount toward a mature rate (often year five), because each renewal exposes the insurer to a longer span of prior acts. Switching from occurrence to claims-made, or vice versa, requires careful coordination of the retro date and tail coverage so no gap opens between the two programs.

Trap: Buying a Supplemental ERP (tail) on an expiring claims-made policy versus buying prior-acts (nose) coverage on a new policy are two ways to bridge the same gap — expect a question on which party purchases which.

What Triggers Coverage: The Two Models

A coverage trigger is the event that activates a liability policy. The two models answer different questions. An occurrence trigger asks when did the injury or damage happen: the policy in force at the moment of bodily injury or property damage responds, regardless of when the claim is later filed. A claims-made trigger asks when was the claim first made against the insured: the policy in force when the claim arrives responds, provided the act occurred on or after the retroactive date.

The occurrence model creates the long-tail problem for insurers. For latent harms such as asbestos exposure or slowly leaking pollution, the injury may be continuous over many years, and courts have applied competing theories to decide which occurrence policies respond: the exposure theory (coverage triggers when the claimant is first exposed), the manifestation theory (when the injury becomes apparent), and the continuous (triple) trigger (every policy from exposure through manifestation responds). These theories explain how a single asbestos claim can reach back across decades of occurrence policies and stack their limits.

The practical consequences favor different parties. Occurrence coverage protects the insured long-term because a policy bought years ago still responds to a claim today and its limits can stack. Claims-made coverage protects the insurer by letting it match premium to claims actually reported each year and close prior years, which is why volatile long-tail lines use it.

Worked scenario: a worker exposed to a product from 2008 to 2012 is diagnosed in 2024 and sues. Under occurrence coverage, the policies from 2008 through 2012 (and possibly later, under a continuous trigger) can each respond, stacking limits across those years. Under claims-made coverage, only the 2024 policy responds, and only if its retroactive date reaches back to 2008. Recognizing which trigger applies and which policy year responds is the core trigger question.

Key Takeaways

An occurrence trigger responds based on when injury or damage happens and can stack the limits of every policy year touched by a long-tail loss, while a claims-made trigger responds based on when the claim is first made and only if the act follows the retroactive date. Courts resolve continuous occurrence losses with exposure, manifestation, or continuous-trigger theories. Bridge a switch between models with a tail on the old policy or prior-acts coverage on the new one.