The FCC has endorsed an "N minus one" (N-1) querying protocol. Under this protocol, the N-1 carrier will be responsible for the query, where "N" is the entity terminating the call to the end user, or a network provider contracted by the entity to provide tandem access.

Thus the N-1 carrier (i.e., the last carrier before the terminating carrier) for a local call will usually be the billing owner of the call.

The N-1 carrier for an interexchange call will usually be the calling customer’s Interexchange Carrier (IXC). An N-1 carrier may perform their own querying or it may arrange for other carriers or third parties to provide querying services on its behalf.