Hi I have IBs PF margin, and I find that the margin use is very non-linear. What I mean by that is, theres only about 15% margin needed, provided small trades are placed, but I find when larger trades are placed (on the same stocks) that the margin is needed is more like about 30%, it seems to happen regularly enough that it seems like some sort of general rule and I was wondering if other users also have this experience.
If you have a single stock position in IB portfolio margin account, the margin will be 30%. You should have a diversified portfolio of 7-8 stocks with about equal market value to get 15% margin. I recommend to go to http://interactivebrokers.com/en/p.php?f=margin, pick "Portfolio Margin" and read. Quote, "Classes with large single concentrations will have a margin requirement of 30% applied to the concentrated position."