Definition:Co-insurance
🤝 Co-insurance is a risk-sharing arrangement in which two or more insurance carriers jointly underwrite a single policy, each assuming a specified percentage of the total risk. Unlike reinsurance, where one insurer transfers part of its exposure to another after the fact, co-insurance involves multiple insurers appearing on the same original policy from inception, each directly liable to the policyholder for their agreed share. This structure is particularly common in large commercial lines placements — property portfolios, major construction projects, and complex liability programs — where a single carrier may be unwilling or unable to absorb the full exposure on its own.
⚙️ In practice, one insurer typically serves as the lead insurer, setting the terms, conditions, and premium rate for the placement, while following co-insurers subscribe to specific percentages of the risk on those same terms. The lead handles claims administration and day-to-day policy servicing, and each co-insurer pays its proportionate share of any claim. In the Lloyd's market, co-insurance functions through the subscription model, where multiple syndicates each take a line on a slip. Outside Lloyd's, brokers often arrange co-insurance panels in markets where capacity for large or unusual risks is fragmented across several carriers.
💡 For insurers, co-insurance offers a disciplined way to participate in attractive business without concentrating too much underwriting risk on a single balance sheet, which supports sound capital management and regulatory solvency requirements. For brokers and their clients, assembling a co-insurance panel can unlock capacity that no single carrier would provide alone, while still delivering one unified policy rather than a patchwork of separate contracts. The arrangement does, however, demand clear coordination — particularly around claims handling and policy amendments — because disagreements among co-insurers can slow resolution and create friction for the insured.
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