What's happening?
Effective March 3, 2026, Bandwidth will begin a phased rollout of passing SIP 603+ response codes to provide you with additional insight into analytics-based call blocking by downstream US carriers and help identify the parties responsible for the block.
What do I need to know?
SIP 603+ is a response code that provides a specific, real-time per-call notification of analytics-based blocking (e.g., calls suspected of being illegal or fraudulent) across US carrier networks. For more information, please see our SIP 603+ FAQ.
What do I need to do?
No action is required, however, we encourage you to monitor SIP 603+ response codes for more insight into your voice traffic. To address improperly blocked calls, Bandwidth offers Number Reputation Management (NRM), a comprehensive solution for addressing improper call blocking and labeling by analytics engines.
Questions?
If you have any questions, reach out to your Bandwidth Support Team!