Expired flour can be safe to use if it is still good, but it wont have the same quality in flavor and texture as fresh flour. The molecular structure of the flour changes when it goes rancid, which can potentially produce harmful compounds. However, most of the time, using expired flour wont make you sick. If the flour smells rancid, stale, musty, or sour, or if it has formed mold, it should be thrown away immediately. Eating moldy flour thats been exposed to moisture can be toxic if consumed. If the flour doesnt show any signs of deterioration and it has been stored properly, it should be fine for a few months past the printed date. However, using expired flour wont yield the same results as fresh flour, especially for self-rising flour, which contains baking powder. In summary, it is best to avoid using expired flour, but if you do, make sure to check for signs of deterioration and discard it if it smells rancid or has formed mold.