I have a Masters in Accounting, so if I can't understand how MB does its statement accounting I must be an idiot. Anyway here is my issue. I called to find out about there margin interest policy. I posed this hypothetical example. An investor has 10k in equity. He buys 15k worth of stock. He will owe interest on the 5k over and above his equity. Easy. Well if the same 10k account were to have 10k in longs and 5k in shorts would the trader owe interest on 5k in this situation. I am told yes by MB. However, this is not what my statement reflects. This is also not what other online brokers have told me. I called MB and spoke to about 3 different people on this and they have to talk to Penson Fin. to get the exact formula. Isn't this something fairly easy they should be able to reconcile??? Also on their platform when you have a short position it shows a negative cash balance. Very confusing.