Sorry if this has been covered, but I couldn't find an answer. Can somenone please explain margin on a short sale? I have an account with IB, and I'm not clear on what margin is required for a short sail. I called the help desk but I don't think he really knew. He claimed that my buying power would actually increase when I put on a short position. That doesn't seem right. What is the margin requirement for a short sale? For example, if I short sell $10,000 worth of xyz, how is my buying power changed ($10,000 will be deposited to my account, but how much more margin will be required)? Thanks for the help.