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SIP response codes

SIP 484 Address Incomplete

Address Incomplete: the number is missing digits.

484

Name: Address Incomplete
Class: 4xx · Client error
Defined in: RFC 3261
Q.850 cause towards the PSTN: 28 · Invalid number format (address incomplete)
Produced from Q.850 causes: 28

When it happens

The PBX sent the call before the user finished dialling (overlap dialling, short dial timeout).
A prefix was stripped by mistake.

What to check

Increase the inter-digit timeout or add a dial plan rule that waits for the full number.
Check number normalisation on outgoing routes.

What the response looks like

SIP/2.0 484 Address Incomplete
Via: SIP/2.0/UDP 203.0.113.10:5060;branch=z9hG4bK776asdhds
From: <sip:101@pbx.example>;tag=1928301774
To: <sip:+15551234567@pbx.example>;tag=a6c85cf
Call-ID: a84b4c76e66710@203.0.113.10
CSeq: 2 INVITE
Reason: Q.850;cause=28;text="Invalid number format (address incomplete)"
Content-Length: 0