Definition
Fill or Kill (FOK) Order
A Fill or Kill order must be executed in its entirety immediately, or the whole order is cancelled; partial fills are not permitted.
FOK is an all-or-nothing instruction useful when a trader needs the full quantity at once, for example to complete a hedge or a basket leg, and a partial fill would be useless or risky. If the full size is not available immediately at the limit price, the order is killed entirely.
FOK differs from IOC, which allows a partial immediate fill and cancels the rest. Because FOK demands complete and instant execution, it tends to fill only in liquid instruments; in thin markets it is often cancelled, so traders use it selectively where execution certainty of the whole quantity matters.
Related terms
- IOC Order (Immediate or Cancel)An Immediate or Cancel order executes immediately against available orders to whatever extent possible, and any unfilled portion is cancelled instantly rather than resting in the order book.
- Day OrderA day order is valid only for the trading session in which it is placed; if it is not executed by the close, it is automatically cancelled and does not carry over to the next day.
- Limit OrderA limit order specifies the maximum price a buyer will pay or the minimum a seller will accept, executing only at that price or better and resting in the order book until it can be filled.
Plain-English explainer from The Dispatch Investors Encyclopedia. General information, not financial advice.