An image forming system includes a detection unit to detect a recording material, having an image formed thereon by an image forming unit, placed on a processing tray, a staple unit, a discharge unit, and a discharge tray. A first mode of the system is to discharge the recording material conveyed from the image forming unit to the discharge tray via the processing tray and a second mode involves waiting for instruction for executing. When the detection unit detects the recording material inserted into the processing tray in the second mode, and a recording material first mode conveying instruction is issued in a state of waiting for the executing instruction after the recording material detection, a discharge operation is performed to discharge the recording material inserted into the processing tray to the discharge tray without the staple unit executing staple processing on the recording material inserted into the processing tray.