If you've just bought a new or used car, you'll want to get an insurance policy as soon as possible. It is not uncommon for insurers to grant a grace period for adding additional vehicles to an existing policy, but it might be as short as 24 hours in some states. This can usually be done either through a representative or online. Also, note that this is an excellent time to investigate if you can receive better prices for your car with a different company. You can compare several policies from different insurers, modify coverage levels as per your requirements, and look up pricing online. You can do this even before buying a car, and the coverage will start the day you drive it off the lot.