An insurance endorsement is just another term for a policy rider. Riders or endorsements are clauses added to an insurance policy that can alter that policy in some significant way. These policy changes usually need to be added to the policy when you first buy it, not later on. They often but not always cost extra each month, and when you actively use the benefit stipulated in the rider it may also incur extra fees. Rider terms should always be read carefully or even reviewed with a financial advisor.