The difference is the coverage trigger. An occurrence policy covers injury or damage that happens during the policy period, no matter when the claim is filed. A claims-made policy responds only when the claim is first made during the policy period, and only for injury, damage or acts that happened on or after its retroactive date. That trigger decides which carrier answers a claim, whether a client needs tail coverage when changing carriers, and what an account manager should compare at every policy renewal.
What Is an Occurrence Policy? Coverage on an Occurrence Basis
Insurance written this way looks at when the injury or damage happened. The ISO commercial general liability (CGL) coverage form CG 00 01 covers bodily injury and property damage caused by an "occurrence" that takes place during the policy period. It defines an occurrence as an accident, including continuous or repeated exposure to substantially the same general harmful conditions.
Hypothetically, if a customer has a slip and fall in a client's store in March 2024 and sues in 2027, the 2024 occurrence policy responds, even if the client has since changed carriers, because coverage stays with the year the incident occurred. The trigger is the date of the injury or damage, not the date of the work. If an electrician wires a building in 2023 and the wiring starts a fire in 2026, the policy in force in 2026 responds through its products-completed operations coverage. For a loss occurring years after a job ends, the contractor needs general liability insurance that has stayed continuous.
What Is a Claims Made Policy?
A claims-made policy flips the trigger. Under the ISO claims-made CGL form, CG 00 02, coverage applies only when the injury or damage happened on or after the retroactive date in the declarations and before the policy period ends, and the claim is first made during the policy period or an extended reporting period. The form treats a claim made against any insured as made when notice of it is received and recorded by an insured or by the insurer, whichever comes first.
Professional liability insurance usually works this way. Lawyers' and accountants' errors and omissions (E&O), directors and officers (D&O) and medical malpractice coverage for physicians are commonly claims-made, because professional negligence claims can surface years after the work. In those policies the trigger is usually a wrongful act rather than an occurrence. Many also require the claim to be reported to the insurer during the policy period, not just made against the insured. Occurrence forms do exist in some classes, including some individual policies for nursing professionals.
How the Retroactive Date Works on a Claims Made Basis
A claim is covered only if the injury, damage or professional error happened on or after the retroactive date (often shortened to retro date). Anything earlier is excluded, even when the claim arrives while the current policy is in force, and a new firm's retro date usually equals its first policy's inception date. When a client moves claims-made coverage to a new carrier, ask the new insurance company to match the original retro date, often called prior acts coverage. If the date advances to when the new policy started, every earlier act loses coverage unless the client buys a tail from the old carrier.
Tail Coverage and the Extended Reporting Period
A tail gives extra time to report claims after a claims-made policy ends. It does not extend the policy period, and it only applies to injury, damage or acts between the retro date and the end of the policy. CG 00 02 provides two versions of this extended reporting period (ERP) when the policy is canceled, not renewed, or replaced with coverage that has a later retro date or a different trigger. The basic ERP is a free tail that applies automatically: five years for claims from occurrences reported to the insurer within 60 days after the policy ends, and 60 days for everything else. The supplemental ERP is an unlimited tail added by endorsement, requested in writing within 60 days after the policy ends, for an additional premium capped at 200 percent of the annual premium.
Professional liability tails are carrier-specific. A tail endorsement is usually sold for a set number of years or with no end date, priced as a onetime cost based on the expiring premium. Some physician liability carriers provide a retirement tail at no charge once age and tenure rules are met. Insurance companies set these terms in their own forms, so read the ERP section before quoting a tail.
Claims Made vs Occurrence Policy: Side-by-Side
| Feature | Occurrence form (CG 00 01) | Claims-made (CG 00 02) |
|---|---|---|
| Trigger | Injury or damage during the policy term | Claim first made during the policy term |
| Earlier events | Not relevant | Excluded if before the retro date |
| After the policy ends | Still responds for its own term | Needs a tail for later claims |
| Pricing | Full rate from year one | Lower at first, rising toward maturity |
| Common uses | General liability for contractors and retailers | E&O, D&O, medical liability, some CGL |
Both kinds of liability policies help cover claims from third parties; what differs is which year's policy provides coverage and how it is priced. Claims-made pricing uses step rating. The first year rate is a fraction of a mature rate because only one year of potential claims can trigger the policy. The rate then rises on a graduated rate schedule, usually reaching maturity in about five years. An occurrence policy is often more expensive at first, while claims-made policy costs climb over time and add the tail at the end.
Hypothetical Example: A Design Firm Changes Carriers
Assume an architect has carried claims-made professional liability with one insurer since 2018, with a 2018 retro date. In 2026 the firm moves to a new carrier for a lower premium, and the new policy shows a 2026 retro date. In 2027 a client sues over a design error on a 2022 project. The new policy will not respond, because the 2022 work predates its retro date. The old policy will not respond either, because the claim came after it ended and no tail was bought. Had the account manager asked the new carrier to honor the 2018 date, or priced the old carrier's tail before the prior policy expires, the gap would not exist.
Agency Checklist: Occurrence Based Policy or Claims-Made?
Use these questions at new business and at renewal:
- Which trigger does the policy form use, and which edition is it?
- What retroactive date is shown, and does it match the prior policy?
- Must the claim be made and reported within the same period?
- What tail options exist, and how long does the client have to buy one?
- Does a contract require a certain trigger or tail period?
Then explain the answer in plain terms. A small business owner buying business insurance for the first time should hear which event must happen during the policy for coverage to apply, when the insurer helps cover a loss, how to report a claim or file a claim, and what happens if the incident occurs after the policy ends. Document the explanation and the client's choice, especially when a client declines a tail.
For further guidance or to review your current strategies, please contact our team for a detailed discussion on how understanding the difference between an occurrence vs claims made form can work for your organization. Whether you're an insurance buyer looking for the right policy or an insurance broker seeking to provide the best advice, we're here to help navigate the complexities of occurrence insurance and claims-made policies.
Frequently Asked Questions
Why Choose an Occurrence Insurance Policy If It Costs More?
Because it keeps protecting the client after it ends. An occurrence policy responds to injury or damage during its term no matter when the claim arrives, so there is no retroactive date to protect and no tail to buy when the client retires, sells or changes carriers. That is useful for long-tail exposures such as completed construction work.
Does the ISO Occurrence Form Ever Need Tail Coverage?
No. A claim reported after an occurrence policy ends is still covered if the injury or damage happened during its term. The insured must still give prompt notice of an occurrence and of any suit, and the claim falls under that year's limits, so keep old policies and declarations pages on file.
Can a Client Move From Claims-Made to Occurrence Coverage?
Yes, but the switch leaves a gap. The new occurrence policy will cover only injury or damage after it starts, and claims for earlier events made after the old policy ends have no home. The client needs a tail from the old carrier. Under CG 00 02, replacing the policy with coverage that is not claims-made triggers the basic ERP.
Who Sets the Retroactive Date?
The insurance company sets it at underwriting. A firm with continuous claims-made coverage can usually ask a new carrier to match its earliest date, if it shows proof of that insurance coverage and no known claims. A first-time buyer usually gets a date equal to the policy's effective date, which means no coverage for earlier work.
What Should an Independent Contractor Check in a Contract?
Read the insurance section for the required trigger and how long coverage must last. Many contracts ask for general liability on an occurrence form, and some require professional liability to stay in force, or a tail to be bought, for a set number of years after the work ends. Match the business liability coverage to those terms before the job starts.
