What it means
Most orders tolerate partial fills. Buy ten thousand shares and the market may hand you six thousand now and the rest later, or never.
An all or none order refuses that compromise, so the instruction stands: fill every share at the stated terms, or fill nothing. The trader's fear is the awkward remnant, since a small partial fill in a thin stock leaves a position too small to matter and too visible to exit cheaply.
Thin markets are the natural habitat for the qualifier, because in illiquid small caps getting full size is the hard part and AON tells the market not to bother with scraps. Some venues suppress AON orders from the displayed book, which can further slow their chance of execution.
Traders often pair the qualifier with a limit price, which caps what the full fill may cost. The cost of the guarantee is execution risk.
An AON order can sit unfilled while the price moves away, because ordinary orders without the restriction take priority in many venues. It is also not the same as immediacy, since standard AON orders may rest in the book waiting for enough size, unlike fill-or-kill orders that demand instant execution or cancellation.
Portfolio managers use it for strategy integrity, since a pairs trade or precisely sized hedge is broken by partial fills. Smart order routers now work large orders in patient pieces while hiding intent, which achieves much of what AON protects without the fill risk, though the remnant problem remains for strict strategies.
Traders should therefore judge success by fills achieved at full size, not by how often the idea was right while the order sat untouched. For a manager watching execution, AON is a completeness guarantee traded for speed, accepting that the plan may simply not happen.
Retail platforms sometimes restrict the qualifier through minimum share counts and session limits, while options and some bond platforms accept it wherever partial execution would distort the structure. Once a full fill arrives, the trade clears and settles normally, so only the path to execution is unusual.
In practice
Real-world examples.
Example
A fund places an AON order for 50,000 shares of a thinly traded stock. Only 20,000 shares are offered at the limit price during the first session, so nothing executes and the order keeps working. The fund accepts the risk that the price drifts higher while it waits, because a partial position would be too small to serve its plan.
Example
A trader structuring a hedge needs exactly 8,000 shares to offset an option position and marks the order AON. A partial fill of 5,000 shares would leave the hedge mis-sized and expose the book to the very risk it was meant to cover. The trader therefore accepts that the order may take several days to fill completely.
Example
An investor's AON order sits unfilled all day in a rising stock, while unrestricted limit orders at the same price execute around it. The investor pays for completeness by missing the early part of the move. Afterwards she decides that AON is worth using only when position size, rather than speed of entry, is the real constraint.
Case study
Seen in the real world.
A made-up biotech investor wants 25,000 shares in a stock trading 10,000 shares a day. This case study is fictional and illustrative. Using AON limit orders over several sessions, she accumulates only complete blocks and avoids tipping the market with visible partial fills. Her broker advises a standing AON buy order priced just below the current offer, so the full block fills only if enough sellers appear at that level.
Over six sessions the order fills in two complete blocks of 12,500 shares, and the investor avoids telegraphing her size to the market. The cost is visible. On two sessions the stock rose and the AON order never filled, which the investor records as the price of completeness rather than a failed idea. Her notes also show that the thesis held, so the discipline of waiting for full size paid off in the position she actually built.
Watch out
Common mistakes.
- Using AON in a hurry; the condition sacrifices speed and priority. If getting filled matters more than completeness, drop the restriction.
- Confusing it with fill or kill; FOK demands instant full execution or cancellation, while AON can rest and wait. Choose by whether patience is acceptable.
- Ignoring venue rules; some brokers restrict size, sessions, or display for AON orders. Confirm how your platform handles the qualifier before relying on it.
Questions
People also ask.
What is an all or none order?
An order that must be executed completely or not at all. The broker cannot partially fill it, so the trader gets the entire intended position or keeps none of it.
When do traders use AON orders?
In thinly traded securities and precisely sized strategies like hedges, where a partial fill would leave an awkward or mis-sized position that defeats the trade's purpose.
How does AON differ from fill or kill?
Fill or kill demands the full order execute immediately or be cancelled. All or none can rest in the market, waiting as long as the session allows for enough size to appear.
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