Tail coverage — formally called the Extended Reporting Period (ERP) — extends the time during which claims can be reported under a claims-made policy after the policy ends. You typically need tail coverage when: you retire and discontinue practice, you sell or close the business, you switch to a different carrier without retroactive-date continuity, or you convert from claims-made to occurrence (rare). Tail coverage is purchased once, at policy termination, and typically costs 100% to 300%+ of the expiring annual premium for a 1-to-3-year tail; “unlimited tail” can cost 200%–500% of annual premium. Don’t surrender a claims-made policy without thinking through tail.