Immediate or Cancel

An Immediate or Cancel (IOC) order is a type of market or limit order that must be executed as soon as it is entered into the trading system; any portion of the order that cannot be filled immediately is automatically cancelled. Unlike a Fill‑or‑Kill order, an IOC allows partial execution, meaning the broker will fill whatever volume is available at the specified price (or better) and discard the remainder.

IOC orders are useful for traders who want to avoid unwanted exposure from lingering unfilled quantities, such as when attempting to sweep liquidity across multiple venues or when entering a position in a fast‑moving stock. For example, placing an IOC limit buy for 10,000 shares at $50.00 will execute only the shares presently offered at that price, and any unfilled shares are instantly removed from the book.