As part of the Federal Communications Commission’s (“FCC”) ongoing efforts to eliminate unlawful robocalls, the FCC has expanded the requirement to block calls that are highly likely to be illegal based on a reasonable Do Not Originate (“DNO”) list to include all U.S.-based providers in the call path. A provider’s DNO list may include only invalid, unallocated, and unused numbers, as well as numbers for which a subscriber has requested blocking. A DNO list need not include all possible covered numbers, but the FCC may find a list unreasonable if it is so limited in scope that it leaves out obvious numbers that could be included with little effort. The deadline for implementing use of a DNO list for call blocking is December 15, 2025.

The FCC has also modified its requirement for terminating providers to provide immediate notification to callers when calls are blocked based on reasonable analytics, specifically requiring exclusive use of SIP code 603+ on IP networks. Terminating providers must cease using the standard version of SIP code 603 or SIP codes 607 or 608 for calls that are blocked based on an analytics program. All providers in the call path must transmit the appropriate code to the origination point of the call, including that SIP code 603+ maps appropriately to ISUP code 21. For TDM networks, ISUP code 21 remains the correct notification code. The deadline for implementing these SIP Code requirements is March 24, 2026.

Please contact Robin Tuttle at [email protected] or Dee Herman at [email protected] if you have questions about implementing these upcoming blocking requirements.

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