I like to write future options with my current broker at a small amount. Never over 20% of my required margin. Profits are small but good commissions kill me being far OTM. I understand this calculated using span + their own requirements. Considering switching to IB and have started the process. IB has much smaller commissions. But their auto liquidation scares me because I cannot find how it is calculated. Specifically, when the bid/ask gets wildly wide or non-existent what is the price of the option calcuated on? Therefore my margin requirement which triggers an auto liquidation? Is it the last? bid/ask? mid? I just dont get it. I've had a few margin calls with my current broker which involved a simple conversation less than 30 seconds. I refunded my account or sold positions to become in compliance but no liquidation ever. Im always hedged and dont want to get caught with my pants down. I'm a conservative trader who doesn't accept a margin increase lightly but as a serious threat let alone a threat of liquidation.