An all-or-none (AON) order is a type of order placed in financial markets that specifies that the entire order must be executed in its entirety or not at all. In other words, if the requested quantity of an asset cannot be filled completely, the trade will be canceled instead of executing a partial order.

The purpose of an all-or-none order is to ensure that the trader receives the exact quantity of assets they desire, without settling for a partial fulfillment. This type of order can be particularly useful for investors who have specific requirements or strategies in mind, such as acquiring a certain number of shares to maintain a particular portfolio balance.

While all-or-none orders offer the advantage of precision, they can also have potential drawbacks. These orders may take longer to execute since they require finding a counterparty willing to fulfill the entire order size. Additionally, there is a risk that the order may not get executed at all if there is insufficient liquidity in the market to fulfill the requested quantity.

Traders should consider their specific needs, market conditions, and potential risks before utilizing all-or-none orders in their trading strategies.