What the distinction is
Every professional liability policy must answer a sorting question when a claim arrives: is this one of ours? Two different forms sort by two different calendars. An occurrence policy looks at when the work was done — if the professional error occurred while the policy was in force, that policy answers, no matter how many years later the claim is made. A claims-made policy looks at when the claim arrives — the policy in force at the moment the claim is made against you is the one that responds, provided the work happened on or after the policy’s retroactive date. Most professional lines today — errors and omissions, professional indemnity, and their trade-named relatives — are written claims-made, so the claims-made rules govern most readers’ actual exposure. Neither form is a defect or a bargain; occurrence coverage is generally priced with its long memory in mind, and claims-made coverage tends to be cheaper in its early years precisely because its reach back is limited and grows as the policy matures. The distinction becomes dangerous in exactly one circumstance: when a professional runs a claims-made program without knowing its calendar rules, because those rules make continuity of coverage itself a coverage term.
Who needs to understand it
Anyone insured on a claims-made form — most professionals reading their own professional liability policy — and most urgently anyone about to change something: switching carriers, retiring, selling or closing a practice, letting a policy lapse in a slow season. In steady years the two forms behave almost identically; claims arrive, the standing policy answers. The distinction shows itself only at transitions, when it is usually too late to repair cheaply. It matters at purchase, too: a cheaper claims-made quote against an occurrence quote is not the same product at two prices — it is two different answers to who pays for a claim about today’s work if it arrives in five years.
Where people get surprised
- The retroactive date is the back wall. Claims-made coverage reaches only work performed on or after that date. Accept a new policy with a fresh retroactive date — a routine-looking carrier switch — and every year of prior work falls outside the new form, while the old policy no longer accepts reports. Careers get silently orphaned this way more often than by any dramatic denial.
- Reporting runs on the policy’s clock. A claims-made claim must be reported during the policy period, or within the short extended window the form allows after it ends. A demand that sits unread across a renewal can fail for lateness alone, regardless of its merits.
- Lapsing is not pausing. Cancel or let a claims-made policy expire without arranging what comes next, and coverage for all past work effectively ends with it — new claims about old work have no policy to report to.
- Circumstances count. Many forms allow — and reward — reporting a known circumstance that may later become a claim. Professionals who wait for a formal demand before mentioning trouble often discover the formal demand arrived one policy period too late.
- Occurrence veterans misread claims-made renewals. A buyer accustomed to occurrence thinking treats each renewal as a fresh start. On a claims-made program the renewal is a continuation — its value lives in the unbroken chain of dates, and breaking the chain is the expensive move.
The tail-coverage trap, in one scenario
A consultant winds down a long practice and retires. The work was insured, without a gap, for its entire life — every premium paid, every renewal on time. What the consultant does not do, in the tidy final month, is purchase an extended reporting period — the endorsement everyone calls tail coverage — which would have kept the door open for claims about past work to be reported after the policy ended. From the day the policy expires, the reporting window closes on schedule. Two years into retirement, a claim arrives from a former client: an error in work performed near the end of the practice, discovered only when its consequences matured. The consultant did nothing careless. The work was insured when performed. And no policy answers — the claims-made calendar assigns the claim to the policy in force when it was made, and there is none. The tail was the only bridge across that gap, it was available exactly once, at the moment of exit, and it was not expensive relative to a career. Every element of the trap is ordinary: a retirement, a skipped endorsement, a slow-developing claim. That ordinariness is why it catches careful people.
The one question to ask your broker
“At every exit I might plausibly make — switching carriers, closing, selling, retiring — what happens to my retroactive date and my right to report claims about today’s work, and what do I need to buy at that moment to protect them?”
Have the conversation before the exit, while the answers can still be arranged. On a claims-made program, the coverage you own is not only the policy — it is the unbroken chain of dates behind it, and the tail that guards its end.
Related reading: Errors and omissions insurance · Professional indemnity insurance