All or none (AON) is a finance term used in investment banking or securities transactions that refers to "an order to buy or sell a stock that must be executed in its entirety, or not executed at all".[1] Partial execution is not acceptable; the order will execute "only if there are enough shares available in a single transaction to cover it".
An all-or-none clause in an underwriting contract or investment prospectus gives a securities issuer the right to cancel an issue in its entirety if the underwriting is not fully subscribed.[2]
AON orders are similar to fill or kill (FOK) orders, but the former focuses on "complete vs. partial fulfillment", whereas the latter hinges on the immediacy of the transaction.[3]