To provide a system and apparatus for forming an image capable of easily administrating development units by assigning a user to each development unit, and to provide a control method therefor.

Cartridge IDs for discriminating respective toner cartridges 41, 42, 43, 44 and user IDs for discriminating users who use respective cartridges 41, 42, 43, 44 are set on an external server 300 or the image forming device 10. The cartridge IDs are stored in cartridge memories 41b, 42b, 43b, 44b. When the user IDs are set, user assignment flags are stored in the memories 41b, 42b, 43b, 44b or in a main body memory 135. When the image forming apparatus receives a print request including the user IDs and cartridge IDs from a host 200, if the flags already assigned to the specified cartridges 41, 42 43, 44 are in the ON state, the device inquires the external server 300 or the main body memory 135 about their IDs, and performs printing with the specified cartridges 41, 42, 43, 44 if they agree with the set user IDs.