The systems and method disclosed herein optimize the deregistration of user equipment (UE) from the 5GC. For example, when the UE operates in single-registration mode, for AMF 3GPP access registration with drFlag attribute set to false (or to be absent) in UDM/UDR, a “new attribute”, singleRegIndication, is defined. The AMF sets the singleRegIndication value to “NO_INDICATION” when there is no N26 interface connection to MME. UDM will not instruct HSS to cancel MME (and SGSN/VLR) if there is an old AMF 3GPP registration for which “NO_INDICATION” or “DEREGISTER_SN” is set as the singleRegIndication value (i.e. the old AMF was already registered with the single registration). Otherwise, the AMF sets the singleRegIndication value to “DEREGISTER_SN” when the AMF has established a N26 interface connection to the old MME. UDM can instruct HSS to cancel the MME (and SGSN/VLR).