# Fill or Kill (FOK) Order Explained: Definition, Key Features, and Example

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> **Definition**
>
> A fill or kill (FOK) order is a type of trading order that requires a transaction to be executed immediately and fully, or else it is canceled.

## What Is Fill or Kill (FOK)?

Fill or kill (FOK) is a conditional type of [time-in-force](https://www.investopedia.com/terms/t/timeinforce.asp) order used in [securities](https://www.investopedia.com/terms/s/security.asp) trading that instructs a brokerage to execute a transaction immediately and completely or not at all. Active traders mostly use this type of order, usually for a large quantity of stock. The order [must be filled](https://www.investopedia.com/terms/m/mustbefilled.asp) in its entirety or else canceled (killed).

A FOK order combines features of both an [all-or-none (AON)](https://www.investopedia.com/terms/a/aon.asp) order and an [immediate-or-cancel (IOC)](https://www.investopedia.com/terms/i/immediateorcancel.asp) order. With large orders, it might take a prolonged period of time to complete, and delaying them can have a significant effect on the stock price, leading to a disruption in the market.

### Key Takeaways

*   Fill or Kill (FOK) orders require the entire order to be executed immediately, or else be canceled.
*   FOK orders combine all-or-none (AON) and immediate-or-cancel (IOC) order characteristics.
*   These orders are typically used by active traders for large stock quantities.
*   FOK aims to minimize price disruption by avoiding partial fills and quick cancellations.
*   While not common, FOK orders provide a way to ensure large trades happen quickly or not at all.

## How a Fill or Kill (FOK) Order Works

The goal of a fill or kill (FOK) order is to have the entire position executed quickly at current prices.  
Without a fill or kill designation, it might take a prolonged period of time to complete a large order. These orders are usually for large quantities, and delaying them can significantly affect a stock's price, possibly disrupting the market.  

Some exchanges require that FOK orders must be executed within seconds of being shown to the market. In this case, a market or [limit](https://www.investopedia.com/terms/l/limitorder.asp) FOK order is like an "all or none" order, but it's canceled immediately if not entirely 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.

However, fill-or-kill trades don't happen often in practice. Other time-frame instructions for trades include immediate or cancel (IOC), which fills what it can immediately and cancels the rest, and [good 'til canceled](https://www.investopedia.com/terms/g/gtc.asp) (GTC), keeping the order open until it's filled at a set price.

## Practical Example of a Fill or Kill Order

Assume an investor wants to purchase 1 million shares of Stock XYZ at $15 per share.  If the investor wants to buy exactly 1 million shares immediately at $15 or better, they should use an FOK order. 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.

> **Article Sources**
>
> 1.  U.S. Securities and Exchange Commission. "[Fill-Or-Kill Order](https://www.investor.gov/introduction-investing/investing-basics/glossary/fill-or-kill-order)."