I called my broker im on the same platform, was told yes i can in my margin acct.... BUT ... for every share shorted i MUST have $2.50 in The acct..... so obviously..... its not really viable.... to short 100,000 shares of a penny stock would require $250,000 in the acct . If your are on T or S.... jump on to the live support chat and discuss it with them, friendly bunch.