Definition
An IOC (Immediate-or-Cancel) order must be executed immediately upon entry; any unfilled portion is cancelled rather than resting in the book. A FOK (Fill-or-Kill) order must be filled in its entirety immediately; if the full size cannot be filled at once, the entire order is cancelled. An AON (All-or-None) order can rest in the order book but will only execute when the full order size can be filled at the specified price; partial fills are not accepted. Under UMIR, AON orders do not have the same protected-order status as visible limit orders, so they do not block a trade-through. Dealers must ensure that the choice of order qualifier matches the client's instruction; using an AON qualifier on a time-sensitive order, for example, could result in the order not executing at all if liquidity is fragmented across multiple marketplaces. These qualifiers are commonly tested as part of order-handling and UMIR best-execution scenarios.
Source
UMIR 1.1 (definitions); marketplace trading rules; CIRO IDPC order-handling requirements
Where this shows up on the CIRE
- Outcome 8.1