The disclosure relates to a communication method and system for converging a 5th-generation (5G) communication system for supporting higher data rates beyond a 4th-generation (4G) system with a technology for Internet of things (IoT). The disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method is provided for a terminal to transmit uplink data without a transmission resource previously allocated by a base station in a next generation mobile communication system. A method by a terminal includes while the terminal is in an inactive mode, receiving a paging message from a base station, identifying a paging identifier included in the paging message, if the paging identifier corresponds to a core network (CN) paging identifier, transmitting a first radio resource control (RRC) message, and if the paging identifier corresponds to a radio access network (RAN) paging identifier, transmitting a second RRC message.