Numbering Resources

Central Office (CO) Code

A Central Office (CO) code or NXX code refers to the second three digits (also called digits D-E-F) of a ten-digit telephone number in the form of NPA-NXX-XXXX, where N represents any one of the numbers 2 through 9 and X represents any one of the numbers 0 through 9. CO codes are also known as an exchange, or prefix, or an NXX.

The North American Numbering Plan Administrator (NANPA) is responsible for the neutral administration of the assignment of North American Numbering Plan (NANP) resources in the U.S. and U.S. territories.

 
Below is a list of helpful tips to assist new service providers in getting started with the CO code request process.

Read the INC guidelines located on the ATIS website at https://www.atis.org/committees-forums/inc/documents/:

• Thousands-Block Number (NPA-NXX-X) & Central Office Code (NPA-NXX) Assignment Guidelines (TBCOCAG)
• Location Routing Number Assignment Practices

Read the Frequently Asked Questions located on the NANPA website at www.nanpa.com under Tools, which provides frequently asked questions to central office code related topics such as the NANP Administration System (NAS) and related forms.

Read the NAS User Registration Guide for Service Providers and Service Provider Consultants located on the NANPA website at www.nanpa.com under Tools, NAS User Guides.

Review the NANPA website at www.nanpa.com, which provides information on items such as the assigned and available CO codes for each NPA.

To request a CO code, your company must have an Operating Company Number (OCN). If your company does not have an OCN, contact the National Exchange Carrier Association (NECA) at www.neca.org to request an OCN.

The following is the list of permitted Company Code Category Types for Numbering Resources:

• Incumbent Local Exchange Carrier            ILEC
• Regional Bell Operating Company             RBOC 
• Competitive Local Exchange Carrier          CLEC
• Personal Communications Service             PCS
• Unbundled Local Exchange Carrier            ULEC
• Wireless Carriers                                     WIRE
• Internet Provider Enabled Services           IPES (only Interconnected VoIP)

To request a CO code, you will need to have a current Numbering Resource Utilization/Forecast (NRUF) on file with NANPA. For more information on how to file an NRUF, visit the NANPA website at www.nanpa.com and select NRUF.

Prior to accessing NAS, you will need to register as a new user by going to www.nanpa.com, select NAS Login and complete the user registration for a service provider.

When requesting an initial CO code, you must provide evidence of certification and proof of facilities readiness per the TBCOCAG. When requesting a growth CO code, months to exhaust must be six (6) months or less and greater than 75% utilization. For information on how to complete a CO code request in NAS, refer to the NAS Central Office Code User Guide available on the NANPA under Tools, NAS User Guides.

When submitting a New CO Code, CO Code Modification or a CO Code Disconnect request to specify an Effective Date preference complete one of the following:

1) For an Effective Date of 52 calendar days from when NANPA processes the request, select “By selecting this checkbox, I acknowledge that I am requesting the earliest possible effective date the Administrator can grant. Please note that this only applies to a reduction in the Administrator's processing time, however the request will still be processed in the order received.” checkbox and the leave the default requested Effective Date as is on the Part 1. 

2) For an Expedited Effective Date, select “Yes” for “Request Expedited Treatment”: 

• For an effective date of 45 calendar days from the date NANPA processes the request leave the default Requested Effective Date and include one of the following: 
• Include a statement that "We are serving as our own AOCN and will waive [1-7] days to update BIRRDS" in the Expedited Explanation field; or 
• Attach a letter from your AOCN agreeing to waive their processing time. 

• For an effective date of 30 calendar days from the date NANPA processes the request leave the default Requested Effective Date and include one of the following: 
• Include a statement that, “We are serving as our own AOCN and Tandem Operating Company and will waive [1-7] days to update BIRRDS” in the Expedited Explanation field; or 
• Attach a letter from both your AOCN and Tandem Operating company agreeing to waive their processing time.

3) For an Effective Date other than the default effective date, enter the requested effective in the Requested Effective Date field.  

Once a CO code has been assigned, routing and rating details must be entered into the TelcordiaTM Business Routing & Rating Database System (BIRRDS).

If you are requesting a CO code in a rate center where Pooling is in place, you must submit your application through PAS. For additional information go to https://www.nationalpooling.com/.

To pool, all carriers must be LNP capable and be set up with the Number Portability Administration Center (NPAC). For information on how to become a NPAC user, go to www.numberportability.com.