Modify Order
Request to modify an order. The order attributes which may be adjusted are Price, OrderQty, OrdType, StopPx, ManualOrderIndicator, CustOrderHandlingInst, and OEOID. Modifies will result in a loss of time priority unless (1) they have no change in Price and also reduce OrderQty or (2) they change the StopPx for a stop order that has not been elected. OrdType may be adjusted from Limit to Market.
Time priority is maintained on a replace/modify order in the following cases:
- A decrease in OrderQty with no other changes
- A decrease in OrderQty, a change to the OEOID and/or the ManualOrderIndicator, and no other changes
- A decrease in OrderQty and/or a change to the StopPx on an unelected stop order with no other changes
- A decrease in the OrderQty and/or a change to the StopPx on an unelected stop order, a change to the OEOID and/or the ManualOrderIndicator, and no other changes.
Changes in OrderQty result in an adjustment of the current order's OrderQty. The new OrderQty does not directly replace the current order's LeavesQty. Rather, a delta is computed from the current OrderQty and the replacement OrderQty. This delta is then applied to the current LeavesQty. If the resulting LeavesQty is less than or equal to zero, the order is cancelled. This results in safer behavior when the modification request overlaps partial fills for the current order, leaving the TPH in total control of the share exposure of the order.
A Modify Order may be issued before the acknowledgement for the previous New Order or Modify Order message is received. The OrigClOrdId on the overlapping modify should reference the ClOrdId of the last message that was sent and not the last acknowledged message. Modify Order requests that merely reduce OrderQty may be overlapped and the existing ClOrdId may be reused. This is the only case where reuse of the ClOrdId is allowed.
A maximum of 1,679,615 Modify Order requests may be made to a single order each trading day. Once the 1,679,615th modification is made, then the next user-generated message on the order should be a Cancel Order request.
The Modify Order message can be used to modify either futures or options orders.