If you hire subcontractors, collecting a certificate of insurance is not paperwork for its own sake. It is one of the clearest ways to confirm whether a subcontractor has active insurance before their work creates a problem you may have to manage. For contractors, that matters because subcontractor risk does not stay neatly with the subcontractor. A claim involving property damage, an injury, or an auto accident can quickly become a contract issue, a payment issue, and a client-confidence issue at the same time. A certificate of insurance, or COI, does not replace reviewing the subcontract itself or the actual policy requirements. But it is still a basic checkpoint. It helps verify that coverage appears to be in place, that the named business matches the party you hired, and that key dates and policy types are visible before work begins. If you want a broader overview of how contractor insurance is structured, start with our Contractors Insurance Explained guide. This article is narrower. It focuses on why COIs matter when subcontractors are part of the job. What is a certificate of insurance? A certificate of insurance is a summary document issued by or on behalf of an insurance carrier or agency. It usually shows the insured business name, policy types, limits, effective dates, and insurer information. In practical terms, it is proof that insurance appears to be active on the date the certificate was issued. That said, a COI is not the policy itself. It does not automatically change coverage, create broader rights than the policy provides, or guarantee that every contract requirement has been satisfied. Contractors get into trouble when they treat a certificate as the full review instead of the starting point. Why do contractors ask subcontractors for COIs? The simple reason is that subcontractors create real downstream risk.