Immediate or Cancel (IOC)

An immediate-or-cancel order, usually abbreviated IOC, must be executed straight away at the requested price or better, and any volume that cannot be filled instantly is cancelled rather than left working. Unlike a fill-or-kill order, which is rejected entirely if the full size is unavailable, an IOC accepts a partial fill and simply drops the remainder. Traders use it when they want immediate exposure without leaving a resting order visible in the market — for example when taking whatever liquidity exists at a level during a news spike. Technically it is a time-in-force instruction rather than a separate order type, and it can be attached to both market and limit orders.