3GPP 23.501 v20.2.0 — the document's own text
5.3.3.3.3 NAS signalling connection Release
Taught in 9. Registration, reachability and paging (The 5G system architecture, in depth), 4. Knowing who you are and where you are (The 5G system architecture, overview).
The procedure of releasing a NAS signalling connection is initiated by the AN node (either 5G (R)AN node or N3IWF) or the AMF. The NG-RAN node may include the list of recommended cells/ TAs / NG-RAN node identifiers for paging, during the AN Release Procedure in the AN (see clause 4.2.6 of TS 23.502 [3]). The AMF stores this information, if provided by the NG-RAN.
The UE considers the NAS signalling connection is released if it detects the AN signalling connection is released. The AMF considers the NAS signalling connection is released if it detects the N2 context is released.