Occurrence vs. claims-made: which policy form actually covers you

One of the most consequential checkboxes on the Acord 25, almost always missed by buyers. The difference between occurrence and claims-made coverage shows up years after the work — when policies have lapsed and the claim window matters.

The difference, in one example

A subcontractor installs an electrical system in 2024. In 2027, a fire starts in that system and damages the building. Two scenarios:

Sub had an occurrence policy in 2024: The 2024 policy responds, even though the claim is filed in 2027 and the policy may have been canceled in 2025. Coverage is locked in by when the event happened.
Sub had a claims-made policy in 2024 that lapsed in 2025: The 2024 policy doesn't respond — the claim was filed after the policy expired. Unless the sub bought tail (extended reporting period) coverage, this is an uninsured loss.

Same event. Same negligence. Different coverage outcome based purely on policy form.

How each form works

Occurrence

Covers events that occur during the policy period.
Claims can be filed years later — coverage is determined by the date of injury or damage.
Standard form for Commercial General Liability and Auto Liability.
More expensive, but cleaner long-term protection.

Claims-made

Covers claims filed during the policy period.
Has a retroactive date — events before the retro date aren't covered.
If the policy lapses or is canceled, coverage stops unless tail coverage is bought.
Standard form for Professional Liability (E&O), Cyber, D&O, and some specialty lines.
Cheaper to start, expensive to maintain continuity over decades.

Catch the policy form on every COI.

COIverify reads the OCCUR / CLAIMS-MADE checkbox on the Acord 25 and flags claims-made policies on lines where your contract requires occurrence coverage.

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What this means for COI verification

On the Acord 25, every coverage row has two checkboxes:

OCCUR (occurrence)
CLAIMS-MADE

For long-tail exposures, your contract should require occurrence coverage where it's available. CGL is almost always occurrence. Professional liability is almost always claims-made — that's industry-standard. What you can do for E&O claims-made:

Set the retroactive dateback as far as the contract requires. A retro date of "date of policy inception" is much weaker than "date of original engagement."
Require tail coverage on cancellation.If the sub cancels or doesn't renew, they should buy a 3–6 year extended reporting period to maintain coverage continuity for past work.
Track renewals carefully.A claims-made policy that lapses for a year creates a gap that can't be closed retroactively.

What contracts should require

CGL: occurrence form. (This is industry-standard, but spell it out.)
Auto Liability: occurrence form.
E&O / Professional Liability: claims-made (no choice), with retroactive date appropriate to the contract scope, plus required tail coverage on cancellation.
Workers' Comp: not occurrence/claims-made; statutory.

Frequently asked questions

What's an occurrence policy?

An occurrence policy covers events that happen during the policy period, regardless of when the claim is filed. If a worker is injured in 2024 under an occurrence policy and a lawsuit is filed in 2027, the 2024 policy still responds.

What's a claims-made policy?

A claims-made policy covers claims filed during the policy period, regardless of when the underlying event happened (subject to the retroactive date). If you cancel a claims-made policy and a claim is filed later, the policy doesn't respond — unless you bought tail coverage.

Why does it matter for a COI?

Construction-defect claims often surface years after the work is complete. With occurrence GL coverage, the original policy responds. With claims-made coverage (most professional liability), if the policy lapsed before the claim, you're uncovered. Always check the policy form on the COI.

Do most COIs show whether the policy is occurrence or claims-made?

Yes. The Acord 25 has a checkbox column for each coverage line: 'OCCUR' or 'CLAIMS-MADE.' Look at it. For long-tail liability exposures, prefer occurrence coverage when you can.

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