In an image forming system of the present invention, a master image forming apparatus
determines, at the beginning of a joint copy job, whether or not a user stamp is
registered at a slave image forming apparatus. If the user stamp is not registered
at the slave image forming apparatus, the master image forming apparatus executes
copying alone. Alternatively, the master image forming apparatus may send the user
stamp to the slave image forming apparatus before the joint copy job. The system
obviates erroneous copying in a joint copy mode and simply executes the joint copy
mode even if the user stamp is not registered at the slave image forming apparatus.
