Definition - What does Additional Insured mean?
An additional insured refers to parties only covered by an insurance policy subsequent to a request from the actual party who is the primary recipient of the insurance. In other words, additional insured parties are added onto a policy.
Insuranceopedia explains Additional Insured
Additional insured parties are commonly named in commercial general liability policies. The reason is because companies often bring in other companies to do work for them on a particular project or event. For example, a contracting firm may hire an electrician to help them with some wiring. In this circumstance, the contracting firm may name the electrician as an additional insured party. This is due to the fact that if the electrician makes a mistake and causes an injury to someone else, then the contracting company could be sued. Additional insured coverage would cover the resulting costs.