I'm trying to use WHATIF-orders to gauge the margin impact of trades before I finally send my orders but the results are more than unreliable. Sometimes it works perfectly and the returned margin impact matches the required margin after the position is opened nicely but
pretty often it doesn't work at all.
I experimented with an order that definitely should have a margin impact - the shortsale of some put options. The what-order returned zero for both the change in initial margin and maintenance margin. I started with just one contract - result zero. Then I started increasing the position size. Two contracts - still zero.
3 contracts - now I suddenly got a nonzero maintenance margin change although it was much too low. When I went to 4 contracts the margin increased but still it was not what I would expect (or what IB would require from me).
Anybody experienced similar?
Despair