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Outbound ANI Requirements

Flowroute has relationships with carriers to connect origination calls to the destination while following industry standards of operation.

When a customer makes an outbound call to an international destination, they must utilize a valid, legitimately assigned domestic North American billing Automatic Number Identification (ANI) (local, not 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. Complaints from receiving carriers are communicated back to the originating carrier which affects the origination carrier's reputation. This may impact a repeat offender's future call completion rates.

Carrier involvement is due to telecommunication regulations that allow carriers to block improperly formatted or invalid ANI’s. An incorrectly formatted outbound ANI may be in 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. Good dialing practices will allow calls to consistently reach the intended destination. Information contained in the P-Charge-info header is restricted to the carrier's needs, and unavailable to the receiving party.

A properly configured PBX will pass the ANI found in the P-Charge-info header. The information provided in that header is confirmed with the outbound call's carrier, where the correct billing data is collected. The below guidelines should be used to help assign and properly format an ANI.

How to identify correct outbound ANI numbers (examples):

  • A National Number that 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 outbound calls, take some time to review the above guidelines. For a complete verification of outbound calls, check the 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. Ensuring the company's adherence to these practices may help agencies, including PSAPs, emergency operations centers, and law enforcement from encountering a block.

(if a P-Charge-info header is not found, or is unable to be changed, please contact a local IT Professional to assist with specific configurations. Flowroute Customer Support is unable to directly assist in configuring any new or established PBX instances.)


Follow-up Resources:

How to identify proper DID formatting:

Formatting Definitions:

SIP Understanding of ANI Formats:

ANI Definitions:

ANI Configure Example: Avaya

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