All-or-none order
Also known as: AON order
An all-or-none order instructs a to fill the entire order in a single transaction or not fill it at all. Partial fills are not allowed, the trade either goes through completely or it does not happen. This differs from a normal order, where a might fill part of the requested shares now and the rest later as more shares become available at the desired price.
The condition addresses a specific problem for large or illiquid orders. If an investor wants to buy a big block of a thinly traded , the order might otherwise fill in pieces over hours or days as small quantities become available, leaving the investor holding a partial position at an average price they did not intend. An all-or-none order avoids that outcome, the investor either ends up with the full position they wanted or none of it.
All-or-none differs from a in one important way, it has no urgency requirement. A must execute immediately and completely or it is canceled right away. An all-or-none order can sit open and unfilled for the rest of the trading day, or longer if combined with a good-til-canceled instruction, waiting for the full quantity to become available. Because this condition restricts how a can fill the order, it typically takes longer to execute than a plain market or , and some only support it for larger orders.