Most states require that you carry your driver's license on you when you are operating a motor vehicle and that you are able to show it to a law enforcement officer upon request.

California states in its Driver's Handbook that you must always have your driver license with you when you drive. CA requires you to show it to any police officer who asks to see it and if you are in an accident, you must show it to the other driver(s) involved.

Many states will cite you for not having your license on you. In Georgia the charge is 'driving without license on person' and if you are able to show your license to the court within a certain period of time the penalty is a small fine. If you have been stopped without having your license on you, you should see if showing your valid one to the court will dismiss your charge.

To find out if you state has a law governing this, contact your local Department of Motor Vehicles, or like state agency, for information.