Timing information for use to determine the timing to discharge a sheet from an image forming apparatus is transmitted. The timing information is relayed, by being edited repeatedly, from a first sheet processing apparatus connected directly with the image forming apparatus to a second sheet processing apparatus which actually processes the sheet. The timing information is edited on each sheet processing apparatus by considering, for example, transit time of the sheet, processing time of the sheet, preparation time for the sheet to get ready to be processed, and the like. The second sheet processing apparatus transmits the timing information to the image forming apparatus. The image forming apparatus determines the discharge timing of the sheet based on the received timing information and discharges the sheet with the determined discharge timing.