A type of time-in-force designation used in securities trading that instructs a brokerage to execute a transaction immediately and completely or not at all. This type of order is most likely to be used by active traders and is usually for a large quantity of stock. The order must be filled in its entirety or canceled (killed). The purpose of a fill or kill order is to ensure that a position is entered at a desired price.
Without a fill or kill designation, it might take a prolonged period of time to complete a large order. In reality, however, the fill-or-kill type of trade does not occur very often. Other methods of instructing a brokerage on the time frame in which a trade is to be executed include “immediate or cancel,” which means to fill all or part of the order immediately, then cancel any part that cannot be filled, and “good ‘til canceled,” which keeps an order open until it is able to be filled at a specified price.