A data communication apparatus that comprises: an authentication means for accepting authentication information that is inputted when a user logs in to the data communication apparatus and for authenticating the user based on the accepted authentication information; a designation means for designating a transmission destination of a file; an obtaining means for obtaining authentication information required at the time of file transmission; the authentication information being the authentication information input when a user logs in to the data communication apparatus or being authentication information input when designation of the transmission destination is performed; a transmission means for transmitting the file to the transmission destination designated by the designation means in a case where the authentication by the transmission destination is successful on a basis of the obtained authentication information; and a registration means for registering for subsequent transmission the transmission destination designated by the designation means, and the authentication information obtained by the obtaining means, characterised in that the data communication apparatus further comprises a control means for prohibiting registration of the obtained authentication information at the time of registration of the transmission destination of the file when the authentication information that is inputted when the user logs in to the data communication apparatus, is used as said authentication information required at the time of file transmission, and for permitting registration of the obtained authentication information at the time of registration of the transmission destination of the file if the authentication information that is inputted when the user logs in is not used as said authentication information required at the time of file transmission. an authentication means for accepting authentication information that is inputted when a user logs in to the data communication apparatus and for authenticating the user based on the accepted authentication information; a designation means for designating a transmission destination of a file; an obtaining means for obtaining authentication information required at the time of file transmission; the authentication information being the authentication information input when a user logs in to the data communication apparatus or being authentication information input when designation of the transmission destination is performed; a transmission means for transmitting the file to the transmission destination designated by the designation means in a case where the authentication by the transmission destination is successful on a basis of the obtained authentication information; and a registration means for registering for subsequent transmission the transmission destination designated by the designation means, and the authentication information obtained by the obtaining means, characterised in that the data communication apparatus further comprises a control means for prohibiting registration of the obtained authentication information at the time of registration of the transmission destination of the file when the authentication information that is inputted when the user logs in to the data communication apparatus, is used as said authentication information required at the time of file transmission, and for permitting registration of the obtained authentication information at the time of registration of the transmission destination of the file if the authentication information that is inputted when the user logs in is not used as said authentication information required at the time of file transmission. <EOS>