The instant presence system authoritatively determines the present communication location of a subscriber, who may be at any of a number of possible locations. When the subscriber changes their location, they can use a subscriber communication device that is operational at their new location to update their point of presence on the telephone communication network. The instant presence system enables the communication network to complete a communication connection from a calling party to the called party with certainty. The calling party therefore can reach the called party with certainty by simply dialing a single listed directory number associated with the called party, relying on the instant presence system to complete the call connection to the called party, regardless of the present location of the called party.