Do all legs execute?
To maintain the integrity of the spread, all legs of the order must fully execute for the transaction to be complete. If all legs do not execute, the order is cancelled and the executed legs are sent to the IB error account. Note that IB will allow partial fills on the quantity of the order as long as the integrity of each unit is maintained. For example if you buy 10 spread orders and only 3 fully execute all legs, we will fill three, put any executed legs from remaining seven units in the IB error account, and re-submit that portion of the order for execution.