A method and system for dynamic service registration, activation and deactivation on a data-over-cable system. A first network device, such as a cable modem with associated service devices (e.g., Voice over Internet Protocol telephones) sends a first message to another network device, such as a cable modem termination system. The first message includes multiple service parameters for a desired service requested by a service device associated with the first network device. The multiple service parameters are extracted from the first message. A service session profile is created for the desired service. The service session profile includes one or more of the extracted service parameters required by the desired service. The service session profile is used by a service server associated with the cable modem termination system to provide a desired service. The service session profile is associated with a deferred inactive service identifier for the cable modem. The deferred inactive service identifier is returned to the cable modem in a second message. The deferred inactive service identifier is used at a later time by a service device associated with the cable modem to activate the desired service and to generate a service event on a service server. The service event may include an authentication, authorization, accounting or other event. A deferred service can be activated and deactivated used even after a network device, such as a cable modem, has already established a session with another network device, such as a cable modem termination system, on a data-over-cable system.