Let's say I have an ES contract and an short 0DTE ATM call that goes ITM. Will my margin change before assignment? Is it broker dependent? If so, who offers intraday through assignment?
If varies by broker. No reason why you can't have an ITM option that delivers the future as long as you have the cash to cover margin. Intraday margin ends at 5pm est but futures and options are marked by the CME at the 4pm est close.
So lets say I have 5K in my account. At the market open I buy ES, simultaneously sell an ATM 0DTE call. I'm using like 1,300 of margin. The call goes and stays ITM until it is assigned and takes the futures away. Will my margin have changed to like 12,000 between 4 P.M. and assignment, thus, causing me a margin call, I presume? I'm trying to improve my return on margin, in case you're wondering.
I'm not sure where you get the $1300 in margin, but at 5pm, the market stops trading. When your broker processes the assignment, you are flat. If that is processed from 5pm to 6pm est or later, is FCM dependent and software dependent. Until that time, you are long one ES. Some third party futures software do not process the assignment until after they get a file from the FCM which can be a few hours after the 6pm est open. You might have a margin call met by the assignment and might not have BP to trade until that time. Ask you broker.
What % of SPAN do they offer for DT? I would think the net margin for an OTM call is close the futures margin until it goes ITM. $1300 is about 10% of Initial ES margin.