NAS 5G UE to AMF 3GPP TS 24.501

5G NAS - Registration Complete

Registration Complete is the UE-to-AMF NAS message used to confirm that the UE has accepted the registration context returned by the network.

Message Fact Sheet

Protocol	nas	Network	5g
Spec	3GPP TS 24.501	Spec Section	8.2.8
Direction	UE to AMF	Message Type	5GMM signaling

Full message name	5G NAS - Registration Complete
Protocol	NAS
Technology	5G
Direction	UE to AMF
Interface	N1
Signaling bearer / channel	NAS signaling / Dedicated NAS message, commonly transported via UL Information Transfer on the access side
Typical trigger	Sent after the UE receives and accepts Registration Accept.
Main purpose	Closes the successful registration exchange and confirms that the UE has stored or applied the context returned in Registration Accept.
Main specification	3GPP TS 24.501, 8.2.8
Release added	Release 15
Procedures where used	5G Initial Registration, Mobility Registration Update
Related timers	T3550

What is Registration Complete in simple terms?

Registration Complete is the UE-to-AMF NAS message used to confirm that the UE has accepted the registration context returned by the network.

Closes the successful registration exchange and confirms that the UE has stored or applied the context returned in Registration Accept.

Why this message matters

Registration Complete is the UE saying the registration success message was received and accepted.

Where this message appears in the call flow

5G Initial Registration

Call flow position: Final UE confirmation after Registration Accept in a successful registration sequence.

Typical state: UE is entering 5GMM-REGISTERED state.

Preconditions:

The UE has received Registration Accept.
Returned registration context has been parsed and accepted.

Next likely message: Normal service activity or optional follow-on NAS procedures

Call flow position

Previous message(s): Registration Accept, DL Information Transfer

Next message(s): Configuration Update Command, PDU Session Establishment Request, Normal registered-state service behavior

Message direction and transport

Sender and receiver: UE to AMF

Interface: N1

Domain: Core-side mobility management message with radio-side transport dependency

Signaling bearer: NAS signaling

Logical channel: Dedicated NAS message, commonly transported via UL Information Transfer on the access side

Transport / encapsulation: NAS 5GS message carried end-to-end between UE and AMF

Security context: Normally sent after NAS security activation, so engineers usually expect integrity protection and often ciphering.

Message Structure Overview

Registration Complete is usually short and procedural.
Its engineering value is less about payload size and more about confirming that the UE accepted the Registration Accept context without error.
When this message is missing, engineers often look backward at Registration Accept handling rather than forward at later NAS procedures.

ASN.1 Message Syntax for 5G NAS - Registration Complete

This message is not typically analyzed as ASN.1 on the wire. It is usually read as a NAS or protocol field structure instead.

Registration Complete is a NAS 24.501 message, not an ASN.1-defined message.

5G NAS - Registration Complete - Example Dump

Registration Complete
  Extended Protocol Discriminator: 5G Mobility Management
  Security Header Type: Integrity protected and ciphered
  Message Type: Registration Complete

How to read this dump

The first check is that the message follows Registration Accept quickly and under the expected NAS security header.
If optional containers are present, confirm they match roaming or policy context.

Important Information Elements

IE	Required	Description
`SOR transparent container`	Optional	Optional container used when steering of roaming information must be returned by the UE.

Detailed field explanation

`SOR transparent container`

Optional container used when steering of roaming information must be returned by the UE.

Presence: Optional

In practice: In practice, compare this field with the original request and with any later release-dependent optional fields so you can see whether the network accepted the same service model the UE asked for.

What to check in logs and traces

Verify Registration Complete is present after Registration Accept.
Check the NAS security header and sequence progression.
If the message is missing, inspect whether the UE rejected or failed to process Registration Accept.
Correlate the message with the AMF clearing T3550 and moving the UE into normal registered state.

Common Issues and Troubleshooting

Registration Accept is present but Registration Complete is missing.

Likely cause: The UE may have failed while processing the returned registration context or the uplink transport path may have failed.

What to inspect: Check Registration Accept contents, UL Information Transfer, RRC stability, and NAS integrity state.

Next step: Compare with a known-good trace and verify whether the UE resets, sends status, or starts a new registration.

Registration repeats even after apparent success.

Likely cause: The network may not have received Registration Complete, or the UE may not have retained the returned context.

What to inspect: Check uplink delivery of Registration Complete and the next AMF-side state transition.

Next step: Correlate with NAS retransmission timers and subsequent Registration Request attempts.

FAQ

What does Registration Complete do in 5G?

It confirms that the UE accepted the context returned in Registration Accept and completes the successful registration exchange.

Who sends Registration Complete?

The UE sends it to the AMF over NAS after processing Registration Accept.

Is Registration Complete protected?

In most successful registration flows, yes. It is normally sent after NAS security is active.

Related message pages

Related Procedures

5G Initial Registration

Related Tools

Use This Reference in Practice

Decode this message with the 3GPP Decoder, inspect the related message database, or open the matching call flow to see where this signaling step fits in the full procedure.