An external terminal transmits a print job to a printout apparatus and also transmits authentication information required for user authentication in printing that involves authentication to the printout apparatus at one time or a plurality of times and at a different time from the transmission of the print job. The printout apparatus identifies the authentication information received from the external terminal as information to be used for the user authentication when a transmission source user of the authentication information and a client user of the print job are determined to be the same on the basis of transmission-source user identification information for identifying the transmission source user and client user identification information for identifying the client user.