Good question. I had a issue a long time ago with that with a broker. I put a small buy in for a shell but the broker had a glitch and a stupid system. They allowed market buys on shells which most brokers I have ever heard of dont allow it.(I dont remember having it a market anyways but they wounldnt accept my argument for that) And they allowed me to buy at extremely high prices on a market buy when I only had a few dollars in there to get some. It was cash account. So they tried getting me to pay thousands of dollars on a 30 dollar trade and I only had like 35 bucks cash.
I asked them how I could go thousands of dollars in the red with a cash account and they were stumped. They ended up eating the fees once I threatened them with going to the court house for mediation.
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