An immediate or cancel order, often shortened to IOC, is an instruction to fill as much as it can right away at your price or better and cancel any unfilled remainder at once, so it never rests in the book.
Last reviewed 5 December 2025 · Educational, not advice
An immediate or cancel order is one of the time in force instructions you can attach to an order. It tells the market to fill as much of your order as it can at this instant, at your chosen limit price or better, and then to cancel anything that did not fill straight away. The defining feature is that nothing is left resting. A normal limit order can sit in the order book for minutes or days waiting for a match, but an IOC acts once, takes whatever liquidity is available at your price right now, and is gone.
An IOC accepts a partial fill, and that is the detail people most often miss. If you ask for one hundred contracts but only sixty are available at your price in that moment, an IOC fills the sixty and cancels the other forty. This is what separates it from a fill or kill order, which is stricter: a fill or kill must execute in full immediately or not at all, so it would reject the whole order rather than take sixty. IOC says take what you can, fill or kill says all or nothing. They sound similar and behave very differently.
The reason to use an IOC is that it combines the price control of a limit order with the certainty of no lingering exposure. You set the worst price you will accept, so you cannot be filled at a number you did not choose, and yet you never leave a resting order that could be filled later when conditions have changed. In a thin or fast moving market that can be useful, because it lets you reach for the liquidity that exists at your price without committing to wait around for more. It is a way of testing the book and acting on it in a single step.
The tradeoffs are simple but real. Because an IOC does not rest, you can walk away with only part of your intended position, or with nothing if no one is offering your price at that instant. You give up the chance of a later fill in exchange for speed and control. Order types also vary between venues, and the same label can behave a little differently from one platform to another, so it is worth checking which order types a platform supports and how it defines them before you rely on an IOC. Knowing your order type, and reading the book first, is the habit that keeps a fill from surprising you.
You send an immediate or cancel buy for 100 contracts at 50 cents. Right now the book offers 60 contracts at 50 or better. The order fills those 60 immediately and cancels the remaining 40 on the spot, leaving nothing resting. A fill or kill order in the same moment would have done the opposite: seeing it could not get all 100 at once, it would have filled none of them.
Illustrative only. Numbers are examples, not a quote or a prediction, and behaviour can vary by platform.
Choosing the right order type does not make a trade win. An IOC can leave you partly filled or unfilled, and the position can still lose. Prediction markets can lose you money. Stake only what you can afford to lose, never to chase a loss, and never on borrowed money. If it stops feeling like a free choice, step back. In the United States you can call or text the helpline on 1-800-GAMBLER or visit ncpgambling.org.
An immediate or cancel order, or IOC, is an instruction to fill as much of your order as possible right away at your limit price or better, and to cancel any unfilled remainder instantly. It does not rest in the order book waiting for a future match.
Yes. An IOC accepts a partial fill. If only part of your size is available at your price right now, it fills that part and cancels the rest. This is the key difference from a fill or kill order, which must fill in full immediately or not at all.
A normal limit order can rest in the book until it fills or you cancel it. An IOC takes only what is available at that instant and cancels anything left, so it never lingers. You keep price control but give up the chance of a later fill.
No. Order types vary by venue, and not every prediction market offers an IOC. Check the order types a given platform supports before you rely on one, since the same name can also behave slightly differently from place to place.
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