VOIP Block Identifier® - Easy Identification of VOIP Phone Numbers

Identify VoIP phone numbers on your collection and marketing lists to help avoid running afoul of Federal Regulations.

Federal Regulations restrict organizations when making unsolicited marketing and collection calls to telephones where the consumer is charged for the call, which includes some VoIP providers. Yet, there is no VoIP phone do-not-call list for tememarketers and collectors to work from. IMS has created a new service to help address that need.

The IMS VoIP Block Identifier® file identifies blocks (first 7 digits of the 10 digit number) of numbers that are assigned to VoIP carriers and then reassigned to consumers as their 10 digit telephone number*. An updated file is made available twice monthly for download and covers approximately 110,000 blocks representing some 110 million phone numbers that are currently assigned or may be assigned to VoIP phones.

*Please Note: It will not identify telephone numbers that have been Ported to VoIP providers from from telephone companies.

Each record on the file contains 3 fields labeled:

  • NPS (area code)
  • NXX (exchange)
  • X (1st digit of the remaining number - the block of 1,000 numbers)

The three fields contain a total of 7 digits that identify a block of 1,000 telephone numbers assigned to a VoIP provider. These 7 digits, representing the area code, exchange and 1st position of the telephone number, must be matched to the first 7 digits of the consumers telephone number. A match indicates that the telephone number has been assigned to a VoIP provider.

A replacement VoIP Block Identification® file is created twice a month, zipped and placed on the web site on or about the 10th and 24th of each month. When the new file is posted, a notifying email is sent to all subscribers.

VoIP Block Identifier®; Frequently Asked Questions


The price for a 12 month subscription to the VoIP Block Identifier®; file is:

  • $4,695 for Service Providers (If you clean lists belonging to others)
  • $1,795 for End Users (If you clean your own lists)

How to subscribe to the VoIP Block Identifier® File:

  • Subscribe now and you will be given a choice to pay immediately by credit card or receive an emailed agreement and invoice.


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