3GPP 24.501 v20.0.0 — the document's own text

8.3.7.12 IP header compression configuration

Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).

This IE is included in the message:

if the UE wishes to re-negotiate IP header compression configuration associated to a PDU session and both the UE and the network supports Control plane CIoT 5GS optimization and IP header compression; or
to negotiate IP header compression configuration associated to a PDU session after an inter-system change from S1 mode to N1 mode when both the UE and the network support control plane CIoT 5GS optimization and IP header compression, and the UE is operating in single-registration mode in the network supporting N26 interface.