ALL OR NONE ORDER (AON)
The AON abbreviation means, “All or None Order” (AON). AON refers to an order made on a financial exchange to purchase and sell a volume of assets for a specific price. It differs from other order types such as a market order or limit order, in that the AON is placed with specific instructions on how the order should be filled.
True to its name, once an AON is placed, it must be either filled in its entirety or not at all. What this prevents is the partial filling of orders and provides the buyer or the seller the confidence of the set execution price for the whole volume.
AON can be used in algorithmic trading to gauge the direction of the market trend and to help partial fill situations. This is a possibility within the context of high levels of volatility with low volumes in a market. One such example is when a flash crash type of event takes place.