A coinsurer is an insurer that takes a fixed share of coverage under a shared insurance arrangement. Each coinsurer is responsible for a stated percentage of premium and loss payment, as set out in the placement documentation.
Why coinsurers are used
Large or unusual risks may be too concentrated for one carrier. Coinsurers split capacity, allowing a single contract to be sold with broader capital support.
Claims and operations
Claims handling is often coordinated through a lead underwriter or lead insurer. Each coinsurer pays according to its participation share and may apply its own claims reporting rules internally.
Relationship to reinsurance
Coinsurance is often confused with reinsurance because both involve sharing risk. The distinction is practical: coinsurance usually shares the policy directly; reinsurance is protection between insurers behind the scenes.