Numbering Resources

456-NXX Codes

NXX codes from the 456 NPA were made available in 1993 (IL-93/08-002) and used to identify carrier-specific services. This was accomplished by providing carrier identification within the dialed digits of the E.164 number. More specifically, the prefix following 456 (456-NXX) identified the carrier. Use of these numbers enabled the proper routing of inbound international calls destined for these services into and between North American Numbering Plan area countries.

In 2017, the Industry Numbering Committee (INC) investigated the use of this resource in their networks and determined that there was no longer a need for the 456 NPA. INC agreed to sunset the ATIS-0300049, International Inbound NPA (INT/NPA/NXX) Assignment Guidelines and age the 456 NPA for five years before the NPA is returned to the general purpose code pool. As of November 2022, the 456 NPA code was made available in the general purpose NPA code pool.

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