An image forming apparatus executes an image forming operation adequately while reducing a cumbersome work of a user of setting the sheet size. A processor of the image forming apparatus controls an image forming portion to form the image on the sheet even if the sheet size included in an image forming job is inconsistent with the sheet size stored in a storage portion. In such a mode, the processor controls a notification portion so as to give notification when a size detection portion detects one of regular sheet sizes and where the sheet size included in the image forming job is inconsistent with the detected sheet size.

The invention provides a paper path structure that is able to perform the following four functions: pass a sheet of paper through the paper path structure with is original orientation maintained; pass a sheet of paper through the paper path structure with its original orientation reversed; stack a sheet of paper in a stack repository with its original orientation maintained; and stack a sheet of paper in the stack repository with its original orientation reversed. The invention also provides a method to operate said paper path structure as well as a stacker and a printer comprising said paper path structure.

A sheet processing apparatus according to the present disclosure includes: an inlet configured to receive a sheet; an outlet configured to eject the sheet; a conveyance mechanism configured to convey the sheet between the inlet and the outlet; a recognition unit configured to recognize the sheet; and at least one recycling chamber configured to store the sheet. The conveyance mechanism includes a first conveyance mechanism configured to convey downward the sheet received from the inlet, and a second conveyance mechanism connecting between the first conveyance mechanism and the outlet and configured to convey upward the sheet conveyed from the first conveyance mechanism. The recognition unit is disposed on a conveyance path on which the sheet is conveyed by the first conveyance mechanism. The at least one recycling chamber is connected to the second conveyance mechanism.

The present disclosure provides an image forming apparatus configured to execute an image forming operation adequately while reducing a cumbersome work of a user of setting the sheet size. A processor of the image forming apparatus configured to execute a mode where the processor controls an image forming portion to form the image on the sheet even if the sheet size included in an image forming job is inconsistent with the sheet size stored in a storage portion. In such a mode, the processor controls a notification portion so as to give notification in a case where a size detection portion detects one of regular sheet sizes and where the sheet size included in the image forming job is inconsistent with the sheet size detected by the size detection portion.