Does anyone have a way to model this? For example 10 naked SPX 1700 puts, uses ~124,000 margin. How do I find out how much margin is used the next day, for example how much less used if the market goes up, and how much more used if the market goes down, by 1%, 2% etc.? I can't really figure out how to work this calculator on the OCC, it keeps giving me bad data. http://apps.theocc.com/pmc/pmc.do
It will depend on the clearing firm as well. Currently in my PM customer account at Apex, they are now looking 50% down in terms of risk for the SPX!, while a Goldman account I have will look down 20%.
The usage I quoted was for IBKR, shows which is 2x TOS which must be 20% down. I am still not sure how much more is used if the market moves down by 2% does that mean I use 10% more margin?
TOS is showing at 2% down your margin would be at 80k and change. It is looking at the new 10% down from there to calculate the loss. 4% down is 101k and so forth.
Can you show a screenshot? I don't use TOS, but maybe I will make an account there if it can help with modeling the margin.
TOS isn't what it used to be but I have found it one of the better option platforms to use. I think you can open a paper account and use most of their features without putting in money (that might have changed when they became part of TD ameritrade). I don't know if you can model portfolio margin in the papertrade account but it will give you a pretty good feel for the software.
Thanks for the screenshot. How did you initially know it was looking at 10% down for that margin use calculation? I speculate IBKR uses 20% down look because it was 2x what you quoted. So from the data a 2% down move in your case increases the margin by ~30%. So in the IBKR case a 2% down move should only move it by 15%, or would it also be 30%?