Fill or Kill
A fill-or-kill order must execute in full immediately or be canceled entirely. Learn what it does, why it prevents partial fills, and when it is useful.
A fill-or-kill order must be executed completely and immediately, or it is canceled entirely. There is no in-between. Either the whole order fills right now, or none of it does. It is an all-or-nothing, right-now instruction.
It is a more specialized order type, useful in specific situations where a partial fill would be a problem. Let me explain what it does and when it earns its place.
All or Nothing, Right Now
Imagine ordering a dozen identical chairs for a dining set, and telling the shop: "I need all twelve today, or I do not want any of them. Do not send me seven and backorder the rest." That is fill-or-kill. You demand the entire quantity at once, immediately, or the whole order is scrapped.
In trading, this matters when you place a larger order. Normally, an order can fill in pieces: you ask for 20 contracts, and you get 8 now, 12 later, possibly at different prices. A fill-or-kill order forbids that. It either grabs all 20 at your price this instant, or it cancels completely and you get nothing.
Why Avoid Partial Fills
For a beginner buying one or two contracts, partial fills are rarely an issue. Fill-or-kill matters more when you are trading larger size or a multi-leg strategy where the pieces must go together.
Larger orders. A partial fill can leave you with an awkward, half-built position and multiple commissions, filled at scattered prices. Fill-or-kill ensures you get the whole thing at once or step away cleanly.
Precision. Some traders want certainty. They would rather have the complete trade at their exact price or none of it, instead of managing a messy partial fill that leaves their plan half-done.
The trade-off is that fill-or-kill is demanding. By insisting on the full quantity immediately, it is more likely to be canceled than a normal order, especially on thinly traded options where the full size may not be available at your price. It buys certainty of completeness at the cost of a lower chance of filling at all.
- A fill-or-kill order must fill completely and immediately, or it cancels.
- It prevents partial fills: all or nothing.
- It is useful for larger or multi-leg trades that must go together.
- It is more likely to be canceled, especially on thin options.
Pop Quiz
Three quick questions to see what stuck. Pick an answer and the explanation shows up right away.
What does a fill-or-kill order require?
Fill-or-kill is all-or-nothing, right now. The whole order fills immediately, or none of it does.
What problem does fill-or-kill prevent?
It ensures you get the whole quantity at once, avoiding an awkward partial fill at scattered prices.
What is the trade-off of using fill-or-kill?
Demanding the full size immediately makes it harder to fill, so it cancels more often than a normal order.
Bottom Line
Fill-or-kill is the all-or-nothing, right-now order. It fills your entire quantity immediately or cancels the whole thing, sparing you from messy partial fills. It shines on larger or multi-leg trades where the pieces need to go together at once.
For a beginner trading small size, you will rarely need it. But when a partial fill would leave your plan half-built, fill-or-kill gives you a clean all-or-nothing outcome, at the cost of a lower chance of filling.
Keep going: the broader menu is order types, and price control comes from the limit order.