what is fill or kill fok 
fill or kill fok is a conditional type of time in force order used in securities trading that instructs a brokerage to execute a transaction immediately and completely or not at all this type of order is most often used by active traders and is usually for a large quantity of stock the order must be filled in its entirety or else canceled killed 1a fok is essentially an all or none aon and immediate or cancel order ioc combined understanding fill or killthe purpose of a fill or kill fok order is to ensure that an entire position is executed at prevailing prices in a timely manner without a fill or kill designation it might take a prolonged period of time to complete a large order because such orders are typically placed for large quantities prolonged execution of the order has the potential to cause significant changes to a stock s price and causing market disruption on some exchanges an fok should be executed within a few seconds of it being shown to the trading community in this context the market or limit order fok is treated similarly to an all or none order with the exception that it is immediately canceled if not completely filled on other exchanges an fok is executed by filling the order with the number of shares that the first bid or offer makes available then any unfilled balance of shares would be canceled in this context the fok is a way for a buyer or seller to fill what is possible then cancel the rest in reality however the fill or kill type of trade does not occur very often other methods of instructing a brokerage on the time frame in which a trade is to be executed include immediate or cancel ioc which means to fill all or part of the order immediately then cancel any part that cannot be filled and good til canceled gtc which keeps an order open until it is able to be filled at a specified price fill or kill exampleassume an investor wants to purchase 1 million shares of stock xyz at 15 per share if the investor wants to buy 1 million shares fairly immediately and no fewer at 15 or better an fok order should be placed assume the order is placed if a broker has more than a million shares in its inventory and would only like to sell 700 000 shares at the 15 price the order would be killed if the broker is willing to sell 1 million shares but only a price of 15 01 the order would be killed on the other hand if the broker is willing to sell the full 1 million shares at 15 the order would be filled instantly also if the broker is willing to sell the full 1 million shares at a better price say 14 99 the order would also be filled 