Skip to main content
A SIP header that identifies the billing number (DID) for outbound calls, enabling accurate call attribution and routing through Telnyx SIP trunks.

​
Header format

The value must be:
  • A valid DID associated with the Telnyx SIP connection
  • In E.164 format (e.g., +15551234567)
  • Wrapped in SIP URI format

​
Use cases

  • Multiple DIDs on a single SIP connection
  • Call detail record (CDR) attribution per DID
  • Billing and usage tracking per number
  • Carrier-side call routing based on originating number

​
Requirements

  • Telnyx SIP connection configured for outbound calling
  • Valid DID ownership and assignment to the connection
  • PBX access to modify dialplan or trunk configuration

​
Troubleshooting

​
Alternative identification methods

For connections sharing authentication credentials: