I'm at a loss for how IB's overnight margin requirement works for non PM accounts. If I have $100k in my account, and at 2 PM I purchase say 2,000 shares of XYZ at $100/share, and at the end of the day XYZ has dropped 1% to $99/share, my equity is $99*2000-$100k = $98k. If RegT Initial Margin is calculated at end of day prices, it will be $199k*0.50 = $99k, I will trigger a margin call ($98k<$99k) based on not satisfying RegT Initial, and shares will be sold off If RegT Initial Margin is calculated based on time-of-trade prices, it will be $200k*0.50 = $100k, which I satisfied at the time of the trade (my equity was $100k at the time of the trade execution), which is what RegT Initial Margin is intended to cover. I ask this because I often trend trade over a period of a week. If RegT is traded using end of day prices, then a small 1-3% fluctuation intraday at 2:1 will cause margin calls at the end of the day, even if RegT is satisfied at the time of the trade. Contrast this with TDA, where, the above situation would not trigger a margin call unless the price drops to the point where I'm at 30% equity (in the scenario above that would be a 28.5% drop) Am I misinterpreting IB's Margin Rules?