A data communication apparatus that is capable of improving operability when inputting authentication information. An authentication unit accepts authentication information inputted when a user logs in to the data communication apparatus and authenticates the user based on the accepted authentication information. A designation unit designates a file transmission destination that is inputted by the authenticated user. A transmission unit transmits a file to the transmission destination inputted. A registration unit registers the transmission destination of the file. A control unit prohibits registration of the authentication information at the time of registration of the transmission destination of the file when the accepted authentication information is used for file transmission, and permits registration of the authentication information at the time of registration of the transmission destination of the file when the inputted authentication information is not used for file transmission.