A method and apparatus recognize an identifier entered by a user. A caller enters a predetermined identifier through a voice input device or a touch-tone keypad of a telephone handset. A signal representing the entered identifier is transmitted to a remote recognizer, which responds to the identifier signal by producing a recognized output intended to match the entered identifier. The present invention compares this recognized identifier with a list of valid reference identifiers to determine which one of these reference identifiers most likely matches the entered identifier. In performing this determination, the present invention compares each character of the recognized identifier with a character in a corresponding character position of each reference identifier in light of a plurality of confusion sets. On the basis of this comparison, the set of reference identifiers is reduced to a candidate set of reference identifiers, from which a reference identifier that matches the input identifier provided by the user.