Claims-made vs occurrence coverage: when must the policy be active?

One-line orientation

Claims-made coverage generally requires a timely claim and a professional act on or after the policy’s retroactive date. Occurrence coverage looks to whether the covered event happened during the policy period.

Key points

• Claims-made (E&O / Professional Liability):

  • The claim must be made or reported while coverage is active, as the policy requires. The professional act must also fall on or after the retroactive date unless full prior-acts coverage applies.
  • Most architectural firms carry claims-made E&O because this is the standard market form for professional liability.
  • Gap risk at retirement: If the policy lapses, any claims filed afterward are uninsured even if the work was done while insured.
    • Solution: tail coverage (also called extended-reporting coverage) — purchased at or before retirement; extends the reporting window for claims arising from past work.
  • Gap risk when switching carriers: The new carrier’s policy covers claims filed after the switch, but by default may not cover errors that occurred before the switch date.
    • Solution: prior-acts coverage — negotiated with the new carrier; picks up pre-switch acts.

• Occurrence-based (CGL / Commercial General Liability):

  • The policy must be in force when the event (incident) occurs.
  • The claim can be filed years after the policy expires — as long as the injury or damage happened during the policy period, coverage applies.
  • No equivalent “tail” problem: once an event occurs during the policy period, it is covered.

• Policy timing summary: The core question is always: “When must the policy be active to trigger coverage?”

  • Claims-made → claim made or reported as the policy requires, and act on or after the retroactive date.
  • Occurrence → active when the event happens.

Confusions / comparison

	Claims-made	Occurrence
Coverage trigger	Timely claim + act within the covered prior-acts period	Policy active when event occurs
Typical use	Professional Liability (E&O)	Commercial General Liability (CGL)
Gap at retirement	Yes — must buy tail/extended-reporting coverage	No equivalent gap
Gap when switching carriers	Yes — must secure prior-acts coverage from new carrier	No equivalent gap
Late-filed claims	Not covered if policy lapsed	Covered if event was during policy period
Exam trap	”When was the error made?” is the wrong question — ask when was the claim filed	”When was the claim filed?” is the wrong question — ask when did the event occur

Claims-made vs occurrence: which date must the policy cover?

Same scenario, opposite result: claims-made keys to the claim date, occurrence keys to the event date.

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Claims-made: a lapse before the claim is a coverage gap — buy tail coverage. Occurrence: covered once the event occurred.

Related

→ pp-insurance-types — the full portfolio including which types use which trigger
→ pp-standard-of-care — what E&O covers and what language makes a claim uninsurable
→ pp-certificate-additional-insured-subrogation — proof of coverage instruments