Fill or kill definition

Fill or kill orders are seldom used, but when they are issued it’s typically to buy a large amount of stock. A small change in price can significantly affect large orders, so in these cases a fill or kill order is ideal to protect a trader’s entire position. Immediate-or-Kill (IOC) orders are more common, as they allow for partial executions of the order to be filled even if the entire order cannot be done. All-or-Nothing orders are also similar to FOK orders, but instead of being cancelled if unable to proceed, they remain good until they can be executed or are cancelled.