All or none order
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All or none order (AON)
All or none order (AON).
When a trading order is marked AON, the broker who is handling the order must either fill the whole order or not fill it at all.
For example, if you want to buy 1,500 shares at $20 a share and only 1,000 are available at that price, your order won't be filled. However, the order will remain active until you cancel it, and so may be filled at some point in the future.