(1) A type of order where the client wants the entire order executed or none of it. (2) A type of best efforts underwriting in which the issuer will sell the entire amount, or cancel the entire issue.
With stock orders for large lots of shares, there is a chance the whole order cannot be filled at once. Choosing the all-or-none option prevents the brokerage from partially executing the order. In some cases there is no disadvantage to filling a partial order, and some brokerages even charge a single commission for multiple fills of the same stock (on the same buy or sell side). But when you want it all or nothing, choose all-or-none.
A type of order instructing the exchange or market maker to execute the entire order quantity at the stated price (or better) or none of it.
At order entry, if it can execute in total, then it executes. Otherwise it stays in the order book until it can execute in total.
This prevents a broker from filling an order in bits and pieces, which can lead to higher commissions because of a minimum cost for each transaction. The transaction must be for the exact number of shares specified.
An order for stock purchase that requires the broker to buy either all of the required shares or not complete the order. An AON order requires special processing and might not be executed unless the stock trades at exactly the target price.
A buy or sell order for stock that instructs the broker to either fill the entire order during a specified time period or not fill it at all.