GlossaryIntermediate
Fill-or-Kill (FOK)
An order instruction requiring the entire order to execute immediately in full, or be canceled entirely with no partial fill.
Fill-or-Kill (FOK) is an order instruction requiring the entire order to execute immediately and in full — if there isn't enough available liquidity to fill the complete order size right away, the entire order is canceled, with no partial fill left resting on the order book.
FOK is useful specifically when a trader needs an all-or-nothing execution guarantee — for example, as part of a strategy where a partial fill would leave an unwanted, mismatched position — rather than accepting whatever partial amount the market can currently fill.
Examples
- A Fill-or-Kill order for a size larger than the currently available liquidity is canceled entirely, rather than partially filling and leaving the remainder unexecuted.
- Traders use Fill-or-Kill specifically when a partial fill would be worse than no fill at all, such as in a strategy requiring an exact, complete position size.