All or None

An all-or-none order is a type of limit order with the added condition that it must be filled in its entirety or not at all. Unlike a fill or kill order, which demands immediate execution, an AON order can rest on the order book and wait for conditions where the full quantity is available at the specified limit price. The order simply will not be executed partially under any circumstances.

The rationale for using an AON order is similar to that for fill or kill: investors who need a specific quantity to implement a strategy — whether a hedging position, an arbitrage leg, or a block accumulation — may prefer to wait for complete execution rather than accept a partial fill that leaves the portfolio in an unbalanced state. AON orders are therefore most common among institutional traders and sophisticated retail investors dealing in larger block sizes.

AON orders interact with market microstructure in a nuanced way. Because they cannot be partially executed, exchanges and electronic communication networks often handle them differently than standard limit orders. An AON order may not receive execution priority over a regular limit order at the same price, since the exchange cannot guarantee the full block will be available at that moment. This means AON orders can sit unfilled even when the market price matches the limit price, simply because the available liquidity at that price is insufficient to fill the entire order at once.

Retail investors should verify whether their broker supports AON orders, as platform support varies. Some platforms accept AON orders for exchange-listed equities but not for over-the-counter securities. The SEC and FINRA require broker-dealers to disclose order-handling and routing information, and investors can review their broker's order routing disclosures — typically published in 'Rule 606' reports — to understand how various order types are handled.

In practice, many retail investors find that standard limit orders satisfy their needs because retail order sizes are small enough that partial fills are the exception rather than the rule. AON orders become a meaningful tool primarily when trade size approaches or exceeds the typical depth of the order book at a given price level.