Definition:Additional insured endorsement
📄 Additional insured endorsement is a modification attached to a commercial general liability or other liability policy that extends coverage to a party beyond the named insured, granting that additional party certain rights under the policy without requiring them to purchase a separate policy. In insurance practice, these endorsements are ubiquitous in commercial relationships — property owners routinely require tenants to add them, general contractors require the same of subcontractors, and event venues demand it from organizers. The additional insured gains protection against third-party claims arising from the named insured's operations, products, or premises, depending on the endorsement's specific language.
🔧 The scope of coverage provided hinges entirely on the endorsement form used. Standardized forms published by the Insurance Services Office (ISO) — such as CG 20 10 (ongoing operations) and CG 20 37 (completed operations) — define the boundaries differently, and insurers sometimes use proprietary forms that may be broader or narrower. A critical distinction is whether the endorsement covers the additional insured only for vicarious liability arising out of the named insured's acts, or whether it extends to the additional insured's own negligence as well. Courts have litigated this boundary extensively, and underwriters must carefully match the endorsement language to the contractual risk transfer obligations specified in the underlying business agreement. The certificate of insurance confirms the endorsement's existence but does not itself confer coverage.
⚡ Failing to properly secure an additional insured endorsement — or securing one with inadequate scope — can leave a party exposed to significant uninsured liability, particularly in construction, real estate, and professional services. For brokers and risk managers, verifying endorsement language against contractual requirements is a core competency and a common source of errors and omissions claims when overlooked. On the carrier side, every additional insured endorsement broadens the universe of potential claimants who can access the policy's limits, which has direct implications for loss reserving and reinsurance recoveries.
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