Fill or Kill Order

A fill or kill order (FOK) is an order that must be executed immediately and in full – otherwise it is cancelled. The complete execution can be made up of several partial fills at the same moment. If the full quantity cannot be executed immediately, however, the whole order is cancelled ("killed") and nothing is traded.

How it works

Fill or kill is an execution condition that is often combined with a price limit. It is offered on many electronic trading venues – in Germany, for example, on the Xetra trading system – and on some forex and CFD trading platforms. It differs from the related "immediate or cancel" (IOC) condition, under which any part of the order that can be executed immediately is filled and only the remainder is cancelled.

Example: a trader wants to buy 1,000 shares at no more than $30 with a fill or kill order. If sellers are offering at least 1,000 shares at $30 or less, the order is executed in full straight away – possibly through several partial fills. If only 600 shares are available at that price, the order is not executed at all, not even for those 600 shares.

Why it matters for traders

Fill or kill orders are useful when a partial execution would be pointless or unwanted – for example, when a strategy only works with the full position size, or when a small remaining position would cause additional fees. In return, the trader accepts that the order may not be executed at all, especially in less liquid markets or for large quantities. A plain market order such as a buy-at-market order, by contrast, is usually filled in full, if necessary at successively worse prices – and unlike a day order, a fill or kill order never waits in the market.