What is a fill-or-kill order?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 3 min
In short
A fill-or-kill order executes only if the entire quantity can be filled immediately; otherwise the whole order is cancelled. It prevents a partial fill from leaving a remainder on the book, but if the condition is not met nothing trades at all.
Key points
- Executes only if the full size fills immediately
- Otherwise the entire order is cancelled
- Never leaves a remainder resting on the book
- Rarely succeeds when the book is thin
Definition
An execution condition requiring the full order quantity to fill immediately; if it cannot, the order is cancelled in its entirety without any partial execution.
Submit a fill-or-kill buy for 10 BTC. If there are 10 BTC of sell orders at or below your price, the whole thing fills; if only 7 BTC are available, not a single unit trades and the order vanishes. All or nothing, so no awkward remainder is left over.
The related condition is immediate-or-cancel, which fills whatever it can and cancels the rest. With 7 BTC available, IOC trades those 7 and drops the remaining 3. Whether the full quantity is mandatory is the only real difference.
Fill-or-kill suits cases where a partial trade is worse than no trade. In thin books or quiet hours, though, the condition frequently fails, and you can end up executing nothing while the market moves on.
Watch out for
- · If the condition fails nothing trades, and the opportunity can pass
- · Support for the condition and its exact semantics vary by exchange
- · Large sizes rarely qualify, making outcomes highly dependent on book conditions