Minimum Quantity And All-Or-None Orders

A large order left as a plain limit order can get picked off in small, inconvenient pieces — ten shares here, twenty there — each fill generating its own commission and administrative overhead, while still leaving the information that a large buyer or seller is present visible in the tape. Minimum quantity and all-or-none instructions exist to control exactly how a large order is allowed to be filled.

A minimum quantity order specifies that any single fill must be at least a stated size (say, 5,000 shares); the exchange or venue simply won't match it against a smaller resting order, even if that means waiting longer to get filled at all. An all-or-none (AON) order goes further, requiring the entire order to be filled in a single execution — no partial fills whatsoever — which is common in blocks and less liquid instruments where a trader would rather not execute at all than end up holding an uncomfortable partial position. Both instructions trade off a lower probability (or slower speed) of getting filled against control over fill size, and both are typically only available on certain venues or order types since matching engines need to specifically support the logic.