One disclosure of the present specification provides a method for using packet switching (PS) data off function in user equipment (UE). The method can comprise the steps of: determining whether a session management (SM) delay time timer or a mobility management (MM) delay time timer is being operated, in a state in which the transmission of a non-access stratum (NAS) request message for an SM is required according to a request for the activation or the inactivation of the PS data off function; and, according to the result of the determination, allowing an NAS layer of the UE to include activation or inactivation state information of the PS data off function in the NAS request message for an SM and transmit the same.