Financial Word of the Day: Fill or Kill (FOK)

Larry Jones
Aug 25
2 min read

Updated: Sep 25

Definition of Fill or Kill

If you like your stock orders the way you like your coffee—exactly how you want it or not at all—then you’ll appreciate the Fill or Kill order. A Fill or Kill (FOK) order tells the market: “Fill the entire order immediately at my stated price (or better), or cancel it right now.” There’s no partial fill, no waiting, and no compromise.

How It Works

Imagine you place an order for 10,000 shares of XYZ at $12.50. With a FOK order:

If all 10,000 shares can be bought instantly at $12.50 or less, the order is filled.
If only part of the order is available, the entire thing is killed on the spot.

It’s clean and decisive: all or nothing, instantly.

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Why Traders Use It

A FOK order can be useful in situations where precision and timing matter most. Traders often use it:

In thinly traded stocks, where liquidity is limited and partial orders could throw off a strategy.
During fast-moving events like earnings or news releases, where hesitation could mean paying more.
When their risk management plan demands an exact position size without slippage.

The Trade-Offs

While FOK orders offer control and discipline, they can also be too rigid. If your price is even a little off or the market doesn’t have enough volume, your order simply vanishes. That can protect you from bad fills, but it also means you risk missing opportunities if the stock later moves in your favor.

How It Compares

It helps to know the difference between FOK and other order types:

All-or-None (AON): Requires the full quantity, but can wait to be filled.
Immediate-or-Cancel (IOC): Fills whatever it can immediately and cancels the rest.
Fill or Kill (FOK): Requires the entire order now or nothing at all.

Takeaway

The Fill or Kill order is for traders who value speed and certainty above everything else. If your strategy demands an exact number of shares at a specific price, and you don’t want to waste a second or settle for less, FOK enforces that discipline. Just remember—it’s either everything you asked for, or nothing at all.