Category: User Permissions: Operator, Trading Call Type: Synchronous

Reduces an order’s quantity without losing priority in the order book. An order’s quantity can only be reduced. The other call that can modify an order — CancelReplaceOrder — resets order book priority, but you can use it to increase an order.

Note: ModifyOrder does not surrender or reset order book priority.


  "OMSId": 0,
  "OrderId": 0,
  "InstrumentId": 0,
  "Quantity": 0 


integer. The ID of the Order Management System where the original order was placed.


long integer. The ID of the order to be modified. The ID was supplied by the server when the order was created.


integer. The ID of the instrument traded in the order.


real. The new quantity of the order. This value can only be reduced from a previous quantity.


  "result": false,
  "errormsg": "",
  "errorcode": 0,
  "detail": "",

The response acknowledges the successful receipt of your request to modify an order; it does not indicate that the order has been modified. To find if an order has been modified, check using GetOpenOrders and GetOrderHistory.



Boolean. The successful receipt of a modify order request returns true; otherwise, returns false. This is the acknowledgment of receipt of the request to modify, not a confirmation that the modification has taken place.


string. A successful receipt of a modify request returns null; the errormsg parameter for an unsuccessful request returns one of the following messages: Not Authorized (errorcode 20) Invalid Request (errorcode 100) Operation Failed (errorcode 101) Server Error (errorcode 102) Resource Not Found (errorcode 104)


integer. The receipt of a successful request to modify returns 0. An unsuccessful request returns one of the errorcodes shown in the errormsg list.


string. Message text that the system may send. Usually null.

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