Say Hello to SIP Code 603+: The FCC’s New Standard for Analytics-based Blocked Calls

The Federal Communications Commission (FCC) has introduced SIP code 603+ as a new standard for indicating analytics-based blocked calls in the U.S., replacing the previous codes 603, 607, and 608. This change aims to create a uniform and consistent way for carriers to signal when a call is blocked due to analytics, allowing callers to more easily access redress with operators for legitimate calls. Carriers are encouraged to begin adopting 603+ immediately, with a mandatory industry-wide implementation by March 25, 2026. While Twilio's Elastic SIP Trunking, Programmable Voice SIP, and Bring Your Own Carrier Trunking products will incorporate the new code, there is no impact on non-SIP Programmable Voice services. The transition to SIP 603+ is designed to simplify the identification of blocked calls due to suspected spam, and most customers will not need to take action unless their systems specifically track the older codes. Twilio advises customers to update their systems to recognize 603+ as carriers transition to this new standard.