IOC and FOK Orders: Immediate Execution Rules for Traders
For educational purposes only; not investment advice.
Direct answer
Section titled “Direct answer”IOC means Immediate-or-Cancel. The order tries to execute immediately. Any portion that cannot execute right away is canceled. IOC can allow partial fills.
FOK means Fill-or-Kill. The order must execute immediately and completely, or the entire order is canceled. FOK is stricter because it generally does not accept partial fills.
These are execution instructions, not magic price-improvement tools.
How it works
Section titled “How it works”An order must pass through broker systems, routing, market centers, matching engines, execution reports, and clearing. The quote on a screen shows available prices at a moment; it does not guarantee that the full quantity is available for every order.
IOC and FOK control time and completeness:
- IOC asks, “What can be executed now at acceptable terms?”
- FOK asks, “Can the whole order be executed now at acceptable terms?”
They are often combined with a limit price. A buy limit sets the maximum price the trader is willing to pay; a sell limit sets the minimum price the trader is willing to accept. IOC or FOK then decides what happens to the unfilled quantity.
Example
Section titled “Example”Suppose a trader sends a buy limit order for 10,000 shares at $25.00.
At that moment, only 6,000 shares are available at $25.00 or better.
With IOC, the order may buy 6,000 shares immediately and cancel the remaining 4,000.
With FOK, the order would cancel entirely because the full 10,000 shares cannot be filled immediately at the required terms.
This distinction matters when a trader can accept a partial position versus when the trade only makes sense if the full size is completed.
- Non-execution risk: strict instructions can result in no trade.
- Partial-fill risk: IOC can leave a smaller position than intended.
- Liquidity risk: visible depth can change before the order reaches the market.
- Spread risk: fast execution can still occur at unfavorable bid-ask conditions.
- Routing risk: broker routing and venue rules affect actual behavior.
- Extended-hours risk: thin liquidity can make IOC/FOK results unpredictable.
- Strategy risk: a complex trade may fail if only some legs or quantities execute.
Common misconceptions
Section titled “Common misconceptions”IOC and FOK do not create liquidity. They only decide what to do if enough liquidity is or is not available immediately.
FOK is not always “safer.” It can prevent partial fills, but it can also prevent any execution.
IOC is not the same as a market order. Price controls depend on whether the order includes a limit price.
Seeing a quote does not prove the full order should fill. Queue priority, routing, hidden liquidity, and rapid quote changes matter.
Related topics
Section titled “Related topics”Sources
Section titled “Sources”- SEC Investor.gov, FINRA, and NYSE: order type, limit order, execution, and market-structure context.