What Is a Certificate of Insurance and Why It Matters A certificate of insurance is proof that you have coverage and details what you are covered for. If you are a contractor, vendor, or service provider, a client may request this document before allowing you to start work. It shows them you are properly insured and reduces their risk. Clients may also request to be listed as an additional insured on the certificate, or ask for provisions like a waiver of subrogation. You do not need to know all