How IOC and FOK Orders Handle Partial Fills

Summary

The discussion explains two time-in-force instructions for an order that may encounter insufficient available liquidity. A fill-or-kill order requires the full requested quantity to execute immediately; if that cannot happen, the order is canceled. An immediate-or-cancel order executes whatever quantity is immediately available and cancels the unfilled balance.

The question frames the distinction with a sell order and a displayed order book, but the reply gives only the general definitions. It does not work through the example’s resulting quantities or prices, and it does not discuss venue-specific handling, routing, or whether an order marked as a market order receives different treatment. In practice, the key distinction is whether a partial execution is allowed: FOK requires all-or-none completion, while IOC permits a partial fill. The actual execution price depends on the available bids and applicable market rules.

Key ideas

• FOK requires the entire order to execute immediately or the order is canceled.
• IOC permits an immediate partial fill and cancels any remaining quantity.
• The defining difference is whether partial execution is acceptable.
• Execution prices depend on the opposite side of the book and market handling rules.

Tags

# Difference between IOC and FOK orders


# Difference between IOC and FOK orders












I am trying to understand the difference between FOK and IOC orders. If I send a market FOK or IOC order to sell 100 shares of StockX - what would happen if the orderbook looked like this?

```
SELL SIDE OF ORDER BOOK 
50 @ 300
25 @ 301
100 @ 302
```

## Answer by JoshK (score 3)

https://quant.stackexchange.com/a/60927

Generally FOK means Fill Entirely or Cancel. IOC means "Fill what you can and then cxl the remainder"

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