They raise margin in crashes and auto liquidate your account at the worst prices... It's an age old trick... They dump huge market orders with your account without even an email
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If you use only your cash, you will never have a margin call. The margin call comes because you borrowed the brokers monies and they charge you interest to do so! Now, you put the broker's monies at risk, they will close your trade for you unless, you put up more monies! The broker will not lose monies on your account. They will make sure you cover it with your losses if need be! This is a lot like gambling in Las Vegas and asking the casino to give you credit so that, you can gamble some more! That is after sustaining huge losses!