A Certificate of Insurance (COI) is a one-page document issued by an insurance broker or carrier that summarizes a contractor's active insurance policies. It typically lists general liability, workers' compensation, auto liability, and any project-specific coverage (Builder's Risk, professional liability) along with policy numbers, limits, effective dates, and the named insureds.
Commercial owners, general contractors, and lenders typically require a COI naming them as additional insured parties before allowing work to start. The COI is informational only — the underlying insurance policy is the actual coverage instrument — but a current COI is the standard proof during onboarding.