Liability insurance typically follows the vehicle rather than the driver. This means that if you allow someone to borrow your car and there is an accident, your insurance will respond as if you were driving. You do not have to contact your agent each time someone borrows your vehicle. Coverage is available automatically for non-residents of your household including family, friends, and co-workers who have a valid license.
One exception to this rule is the frequent availability of your vehicle to another driver. In other words, if you have a family member or a friend whom resides with you, the insurance company will likely require you to list that person on your policy. You will also answer a question on the application that confirms all drivers in the household are listed or excluded.
Most insurance companies will exclude drivers in your household that are not listed as drivers on your policy. Even if the household members have their own vehicles and insurance, the carrier may require that they be listed. This is because anyone who has regular access to the vehicle, even for emergency purposes, is an additional risk that the carrier must account for. In the event a household member is driving your vehicle for any reason and is not listed on the policy, a claim could potentially be denied.