What is an immediate-or-cancel (IOC) order?

An immediate-or-cancel (IOC) order requires the quantity currently available to fill immediately, with any unfilled remainder canceled. In order-book-based crypto markets, the order book records unfilled buy and sell quotes and their quantities. IOC attempts to trade against existing quotes without leaving a remainder waiting.

How does IOC work?

IOC restricts how long an order may wait; a limit order restricts acceptable execution prices. They can be combined: submitting an IOC limit order specifies both price and quantity, and the system immediately matches eligible quotes before canceling the unfilled portion.

A buy order can execute only at the limit or below; a sell order only at the limit or above. If eligible quoted quantity is sufficient, the entire order may fill. If insufficient, only part fills. If there are no eligible quotes, the whole order is canceled.

For example, suppose an IOC limit order to buy a token has a price of 101 USDT and a quantity of 10 units, with these sell orders currently available. USDT is the quote asset. The figures are illustrative, assuming the order passes validation and quotes remain unchanged during execution.

The system first buys 3 units at 100, then 4 at 101, filling 7 units in total. The price of 102 exceeds the buy limit and cannot be matched, so the remaining 3 units are canceled immediately.

Only the 3 unfilled units are canceled; the 7 executed units are not reversed. Their trade value is 100 × 3 + 101 × 4 = 704 USDT, before fees.

How does IOC differ from a regular limit order and FOK?

With identical prices and quantities, the differences are whether partial fills are accepted and whether unfilled quantity continues waiting.

A regular good-till-canceled limit order can fill partially and leave the remainder in the book. This validity setting is commonly called GTC (good till canceled), meaning it remains valid until canceled, and is the default for regular limit orders on OKX. IOC also accepts partial fills but leaves no remainder. FOK, or fill or kill, requires immediate execution of the full quantity; if insufficient quantity is available, the whole order is canceled.

In the earlier example of buying 10 units with a limit of 101, only 7 units are available within the limit. The three settings produce different results:

“Immediate” in IOC therefore does not mean the full buy or sell quantity must execute. It means there is no subsequent waiting stage for a fill.

How are fees charged on IOC executions?

In the order-book trading described above, IOC accepts existing quotes, making its execution role taker. The filled portion incurs the applicable taker rate. Actual rates and calculation methods depend on the product and account.

Canceled, unfilled quantity does not incur execution-based trading fees. In the example, fees are calculated on the 7 executed units, not on all 10 units originally requested.

Frequently asked questions

How does IOC differ from a market order?

IOC specifies whether unfilled quantity may continue waiting. A market order specifies execution against currently available quotes without a trader-set limit. They describe different requirements.

For example, the earlier IOC limit buy order expressly cannot execute above 101. A market order has no such trader-set limit, but may still be subject to platform price protection. Treatment of a market order’s unfilled portion depends on the product’s execution rules.

Related terms

Explore FOK orders, limit orders and market orders, or return to the crypto glossary.

References

• OKX: Basic order types
• OKX: Trading fee rules FAQ