An insurance endorsement is a written modification attached to a base policy that adds, removes, or changes coverage terms. Endorsements are the primary mechanism for customizing a standard policy form to match specific needs — common in homeowners, commercial property, and liability insurance.
Insurance policies are issued on standardized forms approved by state regulators. Endorsements allow departures from that standard form — either broadening coverage (e.g., adding flood or earthquake coverage to a homeowners policy), restricting it (e.g., excluding a specific named peril), or changing key terms like the insured's name or address. In property-casualty insurance, the term 'endorsement' is standard; in life and health insurance, the equivalent modification is typically called a [[rider]]. The distinction is largely convention — both accomplish the same legal function of amending the contract. For business policyholders, common commercial endorsements include: additional insured (adding a landlord or lender as an insured party), waiver of subrogation (preventing the insurer from suing a third party after paying a claim), and hired-and-non-owned auto (extending commercial auto coverage to employees' personal vehicles used for business).
Functionally they are the same — both modify an existing insurance policy. By industry convention, 'endorsement' is used in property-casualty insurance and 'rider' in life and health insurance.
Broadening-coverage endorsements generally increase the premium. Restricting endorsements (exclusions) may reduce it. Some administrative endorsements (correcting a name or address) carry no premium change.