Image forming system that forms images on various types of sheets and controls whether or not to perform printing based on detection results indicating a sheet designated in a job is a different type than the sheet type detected by a sensor

An image forming system comprising:

• an image forming apparatus;
• and
• a server capable of communicating with the image forming apparatus via a network and registering predetermined types of sheets,
• wherein the image forming apparatus comprising:
• a sheet holder configured to hold a sheet;
• a sheet feeder configured to feed the sheet held by the sheet holder;
• a sensor arranged on a downstream side of the sheet feeder in a sheet conveying direction and configured to detect a value regarding a property of a surface of the sheet;
• an image forming assembly configured to form an image on the sheet fed from the sheet holder;
• an input controller configure to input a type of the sheet;
• and
• a display,
• wherein, in a case where a type indicated by user designation information for a first sheet in response to input of a print instruction is different from a type corresponding to the value detected by the sensor for the first sheet, the image forming assembly is controlled not to form an image on the sheet,
• the image forming assembly is further configured to suspend image formation before the image forming assembly completes the image formation, and
• the display is further configured to display a message inquiring whether or not to continue the image formation of sheets not registered in the server, and wherein
• the image forming assembly is further configured to form an image using an image formation condition based on the type indicated by the user designation information for a first sheet without changing the type indicated by the user designation information for the first sheet in a case where a continuation of the image formation is selected, and
• the image forming assembly is further configured not to form an image in a case where a continuation of the image formation is not selected.