Hello all, I have a standard Margin Account with thinkorswim (TD Ameritrade) and have just received a notification that my account is in a "concentration margin call". I checked my equity and it is well over the 50% initial margin requirement, let alone the 30% maintenance requirement. I have searched their site and their is no mention anywhere of a concentration margin call and I've never received one before. Of course, I have sent them an email requesting additional info, but this was a couple of hours ago and I have not yet heard back. I live in Australia and will have to call them soon, but any information you can supply before I call would be of great benefit. The only thing I can think of is that I do have a high concentration of AAPL shares, however these are doing well, so if this was the case it would seem I am being penalised for my majority holding doing well, versus a minor holding such as IMAX. Thank you all. Damen