If you trade a lot, Interactive Brokers has the lowest retail trading cost and the widest variety of securities that you can trade. However, they aren't going to be excited to take your call if you have customer service questions.If all you do is buy US securities and if you don't trade much overall then just use Schwab or another large US broker - avoiding the hassle of trying to track down an annoying tax form is worth $100 extra in commissions. And of course if you are working right now fith Forex - here are the rates of top brokers
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