One of the biggest problems with the regulators is they pass rules but they don't define them. If you call three different clearing houses right now, you will get three different answers as to what is PDT...and how to enforce them. one thing to keep in mind is that if you have 25k in an account, then you lose some $$ and fall to say 24k, all your trades the next day are based on 2:1 ratio, so if you were to buy and sell 100k in securities the next day without having 25k or more, you will get a margin call as if you were at 2:1...that could be a 50k margin call!