I've never found anything in IB regarding this.Isn't that something that is software-dependent? Does TWS not have the ability for that to be selected?
For example, using NT7 you can enforce a top-of-book fill with the following option...
View attachment 296884
By leaving the check-box empty, the NT7 sim engine will try to match realistic market conditions at the time of execution.
As for NT7, Why wouldn't we want the fill not being as realistic as possible?
