| Protocol | nas | Network | 5g |
|---|---|---|---|
| Spec | 3GPP TS 24.501 | Spec Section | 8.2.9 |
| Direction | AMF to UE | Message Type | 5GMM signaling |
| Full message name | 5G NAS - Registration Reject |
|---|---|
| Protocol | NAS |
| Technology | 5G |
| Direction | AMF to UE |
| Interface | N1 |
| Signaling bearer / channel | NAS signaling / Dedicated NAS message, commonly transported via DL Information Transfer |
| Typical trigger | Sent when the AMF cannot accept the registration request because of subscription, roaming, identity, slice, or policy reasons. |
| Main purpose | Stops the current registration procedure and returns the 5GMM cause and any backoff or policy context that explains why registration was not accepted. |
| Main specification | 3GPP TS 24.501, 8.2.9 |
| Release added | Release 15 |
| Procedures where used | 5G Initial Registration, Mobility Registration Update |
| Related timers | T3346 when provided |
| Related cause values | 5GMM cause |
Registration Reject is the NAS message the AMF sends when a 5G registration attempt is refused and the UE must stop the current registration path.
Stops the current registration procedure and returns the 5GMM cause and any backoff or policy context that explains why registration was not accepted.
Registration Reject is the network telling the UE that the current registration attempt is not allowed, along with the reason why.
Call flow position: Negative AMF response when the UE's registration attempt cannot be accepted.
Typical state: UE is still trying to enter a registered mobility-management state.
Preconditions:
Next likely message: Retry, wait, or remain deregistered depending on cause
Call flow position: Negative AMF response when a mobility or periodic registration update cannot be accepted.
Typical state: UE already has or recently had registration context, but the update path is refused.
Preconditions:
Next likely message: Backoff, retry, deregistered handling, or limited service depending on cause
Previous message(s): Registration Request, Authentication Failure, Identity Response
Next message(s): Backoff or retry behavior, Fresh Registration Request, Deregistered state handling
Security context: May be sent plain or protected depending on the exact stage and available NAS context.
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 Reject is a NAS 24.501 message, not an ASN.1 structure.
Registration Reject
Extended Protocol Discriminator: 5G Mobility Management
Security Header Type: Plain NAS
Message Type: Registration Reject
5GMM Cause: PLMN not allowed
T3346 Value: 12 minutes
| IE | Presence | Description |
|---|---|---|
5GMM cause | Mandatory | Primary failure reason explaining why registration was refused. |
T3346 value | Optional | Backoff timer that tells the UE how long it should wait before trying again. |
5GMM causePrimary failure reason explaining why registration was refused.
Presence: Mandatory
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.
T3346 valueBackoff timer that tells the UE how long it should wait before trying again.
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.
Likely cause: The underlying cause is persistent, such as subscription mismatch, roaming restriction, wrong identity context, or barred service.
What to inspect: Check the exact 5GMM cause, slice context, PLMN/TAI alignment, and AMF policy assumptions.
Next step: Troubleshoot by cause rather than retrying blindly, especially if T3346 is present.
Likely cause: The AMF provided T3346 and the UE is correctly backing off.
What to inspect: Check the timer value and compare it with later UE access behavior.
Next step: Validate whether the retry pause is expected instead of treating it as a separate access failure.
It is the AMF's failure response when a registration attempt cannot be accepted.
The 5GMM cause and any T3346 backoff timer.
No. It usually points to mobility-management, subscription, identity, slice, or policy problems rather than radio decode failure.
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.