I have been a long time IB customer and I trade fairly actively. I have observed that IB changes its margin policy from time to time, and without any communication to its clients. Maybe the algos change with new TWS release, whatever it is, the way TWS behaves regarding checking margin changes from time to time. I will write my experience of today: 1) Earlier, TWS didn't use to execute an order if after execution, it will result into a margin call. Today I was fully margined, I was long NQ fully margined, and had a limit order to execute long ES which would have clealy resulted into margin liquidation upon execution. As soon as ES price moved to my limit price, my order executed instead of being cancelled and shortly afterwards IB auto-liquidated it. It resulted into a loss, I had not cared to cancel my standing long ES limit order since I believed it would have been rejected by IB. How can IB change its policy without informing clients? Has anyone else experienced this? This would be a big problem if you are trading hundreds of stocks simultaneously. You will keep getting hit and then auto-liquidated.