Dialed Number Identification Service (DNIS) is a service sold by telecommunications companies to corporate clients that lets them determine which telephone number was dialed by a customer. This is useful in determining how to answer an inbound call. The Telecommunications company sends a DNIS number to the client phone system during the call setup. The DNIS number is typically 4 to 10 digits in length.[1]
For example, a company may have a different toll free number for each product line it sells. If a call center is handling calls for multiple product lines, the switch that receives the call can examine the DNIS, then play the appropriate recorded greeting. Another example of multiple toll free numbers might be used for multi-lingual identification. A dedicated toll free number might be set up for Spanish speaking customers.
With IVR (Interactive voice response) systems, DNIS is used as routing information for dispatching purposes, to determine which script or service should be played based on the number that was dialed to reach the IVR platform. e.g. 0906 123 4567 and 0906 123 4568 may well both connect to the same IVR system but one number may be required to provide a competition service and the other might be an information line. The DNIS is what distinguishes these lines from each other and hence the IVR will know which service to provide to the caller.