Fill-or-Kill Orders: Immediate Execution Without Partial Fills

Summary

A fill-or-kill (FOK) order is a time-in-force instruction requiring an order to execute immediately and completely at its limit price or better; otherwise, the exchange cancels it. The document explains this through order-book examples and contrasts FOK with immediate-or-cancel (IOC), which permits a partial fill, and all-or-none (AON), which requires a complete fill but does not specify immediate execution. It also places FOK alongside market, limit, stop-limit, one-cancels-the-other, and good-till-canceled orders.

FOK can help traders enforce a chosen price and quantity, avoiding partial exposure when only part of the desired size is available. The trade-off is that the order may be canceled entirely, especially in less liquid markets, so a trader can miss an opportunity. The guide describes potential use by day traders and scalpers but provides no performance evidence or execution analysis. Actual order behavior can depend on exchange implementation, and FOK does not remove price or market risk.

Key ideas

• A FOK order must be filled immediately and completely or it is canceled.
• Unlike FOK, an IOC order can execute partially and cancel the remainder.
• AON requires a complete fill but does not impose FOK’s immediate timing condition.
• FOK can control price and quantity while increasing the chance of no execution in thin markets.
• The guide offers order-type explanations rather than evidence of trading performance.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.