Fill-or-Kill (FOK) Order
The Formal Definition
A conditional order instructing the broker to execute the entire order quantity immediately at the specified limit price or better; if not filled in its entirety, the order is canceled.
Order Rule: Total Fill == 100% Instantly, Else Cancel Immediately
Cole Barrett's Reality Check
The Unvarnished Bottom Line"A Fill-or-Kill order is an all-or-nothing trade. You use it when you need 500 options contracts right now to hedge a position, and you won't accept getting filled on only 5 contracts and paying a full minimum ticket fee for a partial fill."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Placing an order for 2,000 shares of a low-volume equity
| Execution Metric | Fill-or-Kill (FOK) Limit Order | Standard Day Limit Order |
|---|---|---|
| Fee / Rate | Single ticket fee | Fixed ticket minimum |
| Spread / Buffer | Only 800 shares available at limit price | Filled 15 shares, remaining 1,985 unfilled |
| Execution / Status | Entire order canceled instantly with zero execution | Billed full ticket fee on a tiny 15-share fill |
| Total Cost / Result | Avoided an unwanted partial fill | Stuck paying fees for an incomplete position |
How Brokers Weaponize This Term
Retail platforms often leave advanced execution tags like FOK and IOC off their order tickets, forcing users into standard orders that execute in small partial lots that run up per-trade fees.
Broker Evaluation Matrix
Cole Approves
Interactive Brokers: Supports all advanced institutional order parameters, including FOK, IOC, and GTC routing.
Read Audit →Cole Flags / Avoids
Basic Mobile Investing Apps: Omits all-or-nothing execution tags, resulting in unwanted partial fills.
View Trap Details →Frequently Asked Questions
What is the difference between Fill-or-Kill (FOK) and Immediate-or-Cancel (IOC)?
FOK requires the entire order to fill immediately or cancel completely. IOC fills as much of the order as possible right away and cancels any remaining balance.
When should you use a Fill-or-Kill order?
Use FOK when trading illiquid options or micro-caps where a partial fill creates position imbalances and unnecessary commission overhead.