TL;DR

Occurrence form responds to injuries that happen during the policy period regardless of when the claim is made; claims-made form responds only to claims made during the policy period. For medical device manufacturers with 10 to 20 year implantable tails, occurrence-form is materially more valuable. For pharmaceutical operators, the choice depends on sponsor MSA demands and the manufacturer's appetite for tail coverage at renewal.

Policy form comparison

Occurrence vs claims-made. Sponsor MSAs care about the difference.

The form of an insurance policy - occurrence or claims-made - determines whether the policy responds to a claim. Most sponsor MSAs in life sciences require occurrence form for CGL and products liability specifically because product liability claims can surface years after the manufacturing date, outside any claims-made policy that has since lapsed.

Professional liability, D&O, EPLI, and cyber are typically only available on claims-made. The implication: contract operators run a mixed portfolio of occurrence (CGL, products, property, auto, WC) and claims-made (professional, D&O, cyber). The mix is normal. The mistake is treating them interchangeably at renewal or carrier change.

Side-by-side

Eight dimensions of the trigger and aftermath.

Dimension

Occurrence Form

Claims-Made Form

Trigger

Loss event happens during the policy period. Claim can be reported years later.

Loss event AND claim report both happen during the policy period (subject to retroactive date and ERP).

Typical lines of coverage

CGL, products liability, workers comp, auto, property.

Professional liability / E&O, D&O, EPLI, fiduciary, cyber, medical malpractice.

Sponsor MSA requirement (CGL)

Required by near-universal sponsor MSAs in life sciences. The standard.

Generally not acceptable for CGL/products. Occasionally negotiable for new operators or specialty risks if retro date is sufficiently old.

Tail coverage (ERP)

Not needed. The policy that was in force when the loss occurred responds whenever the claim is reported.

Critical when transitioning carriers or non-renewing. Without it, claims reported after expiration are uncovered.

Retroactive date

Not applicable.

The earliest date for which acts will be covered. Should generally match the operator's start of operations or earlier.

Premium pattern

Premium is typically higher in year one but stable thereafter.

Step-rated - premium rises 25%-40% per year for the first 4-5 years until mature, then stabilizes.

What happens at carrier change

New carrier issues new policy. Old carrier remains on the hook for prior occurrences. No tail purchase needed.

Operator must either (a) buy tail from expiring carrier, (b) negotiate prior-acts coverage with new carrier, or (c) accept the coverage gap. Tail typically priced at 100-300% of expiring premium.

Best practice for life sciences contract operators

Occurrence form for everything that can be written occurrence: CGL, products, property, auto, WC. Standard sponsor MSA expectation.

Claims-made only for lines where occurrence is not commercially available (D&O, cyber, professional liability). Maintain retroactive coverage and budget for tail.

The tail-coverage trap

Claims-made transitions are where coverage gaps happen.

The most common claims-made failure mode: an operator non-renews a professional liability or cyber policy without buying tail, assumes the new carrier covers prior acts, and discovers months later that the new policy's retroactive date excludes the relevant period. Claims arising from acts in that uncovered window are denied by both carriers.

The fix is mechanical but easy to miss: at every carrier change on a claims-made line, the operator either purchases tail from the expiring carrier or negotiates a sufficiently old retroactive date on the new policy. Tail prices range from 100% to 300% of the expiring annual premium - substantial but necessary.

Frequently asked

Common questions about occurrence vs claims-made forms

What is the difference between occurrence and claims-made insurance forms?

An occurrence policy covers losses that happened during the policy period, regardless of when the claim is reported. A claims-made policy covers losses that are both incurred and reported during the policy period (with an optional retroactive date for prior acts and an optional extended reporting period for tail coverage). For life sciences, occurrence is generally preferred for products liability; claims-made is standard for professional liability, D&O, and cyber.

Why do sponsor MSAs require occurrence form CGL?

Sponsors require occurrence form CGL because product liability claims can surface years after the manufacturing date - outside any claims-made policy period that has since lapsed. An occurrence-form policy in effect during manufacturing covers the claim whenever it is reported. This is materially safer for sponsors and now a near-universal MSA requirement.

Are claims-made products liability policies ever acceptable?

Some specialty carriers write products liability on a claims-made basis with sufficient retroactive coverage and tail. Sponsors sometimes accept them when the retroactive date is sufficiently old and the tail is purchased through any program transition. But occurrence form is overwhelmingly the standard, and switching to claims-made mid-program creates a coverage gap unless tail is purchased.

What happens if my CGL was claims-made and I switch to occurrence?

You need to buy tail coverage (an extended reporting period endorsement) on the expiring claims-made policy to cover claims reported after the switch but arising from prior-period acts. Failing to do this leaves a gap: the new occurrence policy does not cover prior acts, and the expired claims-made policy does not cover late-reported claims.

Why is professional liability typically claims-made?

Professional services exposure is harder to underwrite on occurrence form because the underlying act and the resulting claim can be separated by years (e.g., a clinical protocol error in 2024 surfaces as litigation in 2028). Carriers control this exposure by writing claims-made, requiring the act and the claim to both occur during the policy period, and offering retroactive coverage for prior acts on a negotiable basis.

How does tail coverage (extended reporting period) work?

Tail coverage (ERP) extends the time window during which a claim can be reported under a claims-made policy after the policy has been cancelled or non-renewed. It is typically priced at 100-300% of the expiring annual premium and is the only way to preserve coverage when transitioning to a new carrier or exiting a line of coverage entirely.

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