Procedures, systems, and devices for addressing quality of service (QoS) during an intersystem change of a wireless transmit/receive unit (WTRU) are discussed herein. A WTRU may send a protocol data unit (PDU) modification request to a network node, such as a session management function (SMF) device, indicating support for reflective quality of services (RQoS). In response to the modification request, the WTRU may then receive an acknowledgement, after which the WTRU may then be able to send data for a PDU of a specific RQoS. The RQoS may be specific to a single PDU or a plurality of PDUs. The modification request may include Session Management (SM) and/or Mobility Management (MM) information. The modification request may be included in an attach procedure or a tracking area update (TAU).