Fill or kill is an order instruction that must be executed in full and at once, or cancelled entirely, with no partial fill.
Last reviewed 6 September 2025 · Educational, not advice
Fill or kill is a condition you can attach to an order that tells the market exactly how you want it handled. The instruction is all or nothing, and at once. The order must be filled in full immediately at your price or better, and if the whole quantity cannot be matched in that instant, the entire order is cancelled and nothing trades. There is no half measure. You either get everything you asked for straight away or you get none of it.
The reason this instruction exists is control over two things at the same time, completeness and speed. A trader using fill or kill is saying that a partial position is not what they want. Perhaps they need the full size to do what they planned, or they do not want to be left holding an odd remainder, or they want to avoid their order resting in the book and moving the price as it fills piece by piece. Fill or kill removes all of that. It either completes the whole order in one go or disappears.
It helps to place fill or kill alongside its close relatives. Immediate or cancel also demands instant execution, but it allows a partial fill and simply cancels whatever cannot be filled right away, so you might end up with part of your order. A good till cancelled order takes the opposite stance on time, resting in the book and staying live across sessions until it fills or you cancel it. Fill or kill is the strict one on both counts. It rules out partial fills and it rules out waiting, demanding the whole quantity now or nothing.
The trade off is real. In a thin market where there are not enough contracts available at your price, a fill or kill order will often simply be cancelled, so you can end up not trading at all. You gain certainty that you will never be left with an awkward partial position, and you pay for it with a higher chance that nothing happens. Whether that suits you depends on why you are trading and how liquid the market is. One last point, the order types a venue offers vary, and not every platform supports fill or kill, so check the order options where you trade. Related ideas include a partial fill, when only part of an order executes, and the limit order, which sets the price your order will accept.
Suppose you want exactly two hundred contracts at fifty cents and you send a fill or kill order. If two hundred are available at fifty cents or better at that instant, the whole order fills and you are done. If only one hundred and twenty are available, the order does not fill the hundred and twenty and leave the rest. Because it is fill or kill, the entire order is cancelled and you trade nothing, leaving you free to try again or rethink your size.
Illustrative only. Numbers are examples, not a quote or a prediction, and exclude fees. Available order types depend on the platform.
An order type controls how a trade is handled, not whether it is a good idea or an outcome is likely. Fill or kill can leave you not trading at all in a thin market. 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.
A fill or kill order is an instruction that must be executed in full and immediately, or cancelled in full. There is no partial fill. If the whole quantity cannot be matched at once at your price or better, the entire order is cancelled and nothing trades.
Both demand immediate execution, but immediate or cancel allows a partial fill and cancels only the unfilled remainder, while fill or kill requires the entire quantity to fill at once or nothing trades. Fill or kill is the stricter of the two, since it rules out partial fills.
It suits a trader who wants the whole size or none of it, for example to avoid being left with an awkward partial position or to control the price across the full order. The trade off is that in a thin market the order may simply be cancelled, so you get certainty of all or nothing at the cost of often not trading.
No. The order types a venue offers vary, and not every platform supports fill or kill. Some offer immediate or cancel, good till cancelled, or other instructions instead. Check the order options in the platform you use rather than assuming a particular type is available.
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