Abstract: A technique for coordinating the registration of a terminal (UE) in circuit-switched (CS) and packet-switched (PS) domains of a multi-operator core network (MOCN) with multiple core networks (CN) is described. According to a method approach, a notification message indicating the necessity of coordinated CS and PS registrations for a terminal (UE) is received from a first core network (CN). In a next step, and based on a global permanent identity (IMSI) associated with the terminal (UE), a second core network (CN) responsible for CS and PS registrations is determined. A registration message for coordinated CS and PS registrations is then sent to the second core network (CN) that has been determined based on the global permanent identity (IMSI).