What Is Fill or Kill (FOK)?

Fill or kill (FOK) is a conditional time-in-force order used to trade stocks, forex, metals, and energies. When a trader/investor uses this type of order, a broker must immediately execute an entire order or cancel it. Partial closing or opening of a position on a FOK order is not allowed. The order can be executed only in the stated volume. A FOK is essentially an all-or-none (AON) and immediate-or-cancel order (IOC) combined.

Understanding Fill or Kill

Traders use Fill or Kill (FOK) orders to ensure that the whole order gets executed in the shortest period. If the trader uses another type of order, it might take a long time to pack the entire position. Therefore, large quantity non-FOK orders can cause price changes or market disruption due to prolonged execution. That is why market members who trade with a large capital prefer using the Fill or Kill type of order.

Fill or kill order vs. Immediate or cancel order

However, the fill-or-kill type of trade does not occur very often. Instead, traders prefer using "immediate or cancel" (IOC) or "good till canceled" (GTC) type of orders. IOC allows filling a part of the order immediately. GTC keeps the order open until a position is filled at a special price.

Fill or Kill Example

Assume a trader wants to open a long trade of lots in XAU/USD at $1800 per lot. A FOK order should be placed if the trader wants to purchase 1000 lots immediately, and no fewer, at $1800 (or lower). If a broker can sell 1000 lots of XAU/USD for $1800 per lot or less, the order will be filled. On the other hand, if a broker does not have 1000 lots of XAU/USD or does not want to sell them for $1800 or cheaper, the order will be killed.