An all or none order requires the entire specified quantity to execute or none of it to execute. The AON condition prevents partial fills, but does not by itself require immediate execution.
What happens when liquidity is insufficient?
Suppose a supported market receives an AON buy order for 100 tokens at a stated limit price. If only 60 tokens can be filled within the permitted terms, the order does not buy those 60. It can wait for an eligible full execution while it remains valid, subject to the venue’s handling rules and the order’s expiry.
The quantity condition and price condition are separate. AON controls completeness; an accompanying limit price controls the acceptable execution price. Neither creates the missing liquidity or guarantees that a match will occur.
AON versus FOK and IOC
Fill or kill, or FOK, combines a full-quantity requirement with immediate execution or cancellation. Immediate or cancel, or IOC, allows an immediately available partial fill and cancels the remainder. AON therefore should not be used as a synonym for either instruction.
Availability, minimum sizes and matching priority vary across platforms and products. A full-size condition can delay or prevent execution, so an accepted AON order is not a completed trade.