Image forming apparatus, method for controlling the same, and non-transitory computer-readable storage medium

A control method for an image forming apparatus which includes a feeding unit configured to feed a sheet, an image forming unit configured to form an image on the sheet fed from the feeding unit, a plurality of stacking trays on which insert sheets to be inserted between sheets are stacked, an insert unit configured to feed an insert sheet using a stacking tray of the plurality of stacking trays as a feed source and to convey the insert sheet for merging downstream of the image forming unit, detection units configured to detect amounts of insert sheets stacked on the plurality of stacking trays, respectively, and a controller configured to start feeding of a sheet from the feeding unit without confirming a presence or absence of an insert sheet to be inserted before the sheet in a case in which an amount of insert sheets stacked on the stacking tray as the feed source is higher than a predetermined amount, wherein the insert unit switches the feed source from the stacking tray to another stacking tray in a case in which the insert sheets stacked on the stacking tray as the feed source become absent, the control method comprising:

• determining, in a case in which the amount of the insert sheets stacked on the stacking tray as the feed source is lower than the predetermined amount, whether another stacking tray on which an amount of insert sheets is higher than the predetermined amount is present;
• starting feeding a sheet from the feeding unit without confirming a presence or absence of an insert sheet to be inserted before the sheet when the other stacking tray is present;
• and
• starting feeding the sheet from the feeding unit after confirming the presence or absence of the insert sheet to be inserted before the sheet when the other stacking tray is absent.