Embodiments of the present application provide a charging method, a charging device, a charging system, and an authentication device. According to the technical solutions provided in the embodiments of the present application, when the available service volume of the user is not enough at the time close to the tariff switch point, the operation of forcing a user to go offline may be performed selectively, depending on the specific situation. Therefore, the operation of forcing a user to go offline can meet requirements of increasingly complicated charging policies of the operator.