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Outbound ANI Requirements

Flowroute provides customers with the option to purchase and use International local and Toll-free inbound numbers (ITL, ITFS) in addition to domestic local and Toll-free numbers. Flowroute has relationships with carriers to connect your calls to your destination while following industry standards of operation. 

When a customer makes an outbound call to an international destination, they are required to utilize a valid, legitimately-assigned domestic North American billing Automatic Number Identification (ANI) (local, non-Toll-free). This guideline would remain in place even if a DID purchase from Flowroute is an International local/Toll-free. 

The use of any invalid, inaccurate, or incorrectly formatted US billing number ANI may prevent outbound calls from connecting to their intended destination. This intervention is due to telecommunication regulations that allow carriers to block improperly formatted or invalid ANI’s. An incorrectly formatted outbound ANI can be discovered as a misconfigured PBX or an intentional change of the outbound ANI used to mask the call's originator. 

The ANI will need to pass validation before the calls are connected with the intended destination number. Using good dialing practices will allow for calls to consistently reach the intended destination. Below will help you assign and properly set your ANI. 

How to identify correct outbound ANI numbers (examples):

  • A National Number which is no less than 10 digits and prepended with the country code "1"
  • Properly formatted NPA (area code) or NXX (telephone exchange) number without a 0 or 1 as the 1st or 4th digit.
  • A valid and in-service 10 digit number. This guideline does not include NPAs without an NXX assigned, such as those operating as a 3 digit service number. (ie. 411, 311, 911 e.t.c.)


To responsibly prepare your calls, take some time to review the above guidelines. For a complete verification of outbound calls, check your internal logs to confirm the provided ANI is adhering to the guidelines above. 

Efforts must be made to avoid blocking calls from public safety entities. By ensuring your company's adherence to these practices, you may help agencies, including PSAPs, emergency operations centers, or law enforcement, from encountering a block.

If you are being required to pass an International ANI on outbound calls, please contact Flowroute Customer Support, and provide your use-case. We will work with you to verify if this is permissible for your needs. 


Follow up Resources: 

How to identify proper DID formatting:

Formating Definitions:

SIP Understanding of ANI Formats:

ANI Definitions: