Sheet buffer apparatus, post-processing apparatus, control method, and image forming apparatus

A post-processing apparatus which performs post-processing for a plurality of sheets received from an image forming unit, the apparatus comprising:

• a sheet conveyance unit configured to convey a sheet received from said image forming unit, along a conveyance path;
• a sheet stacking unit configured to stack a plurality of sheets conveyed by said sheet conveyance unit;
• a post-processing unit configured to perform post-processing for a sheet bundle including the plurality of sheets stacked by said sheet stacking unit;
• a buffer unit, arranged upstream of said sheet stacking unit, configured to retain one or more sheets and to overlay the one or more sheets retained and a succeeding sheet;
• an acquisition unit configured to acquire sheet information for determining whether a sheet is inhibited from being retained by said buffer unit;
• and
• a control unit configured to control, based on the sheet information of an (N+1)th sheet, said buffer unit regarding whether said buffer unit should retain an Nth sheet, in a case where an Nth sheet is not inhibited from being retained by said buffer unit.