Brokerages like OX rely on risk files from the exchanges when they calculate your initial margin. The exchange risk files have a ton of info in them like futures price, option price, volatility, delta, and days to expiration, to name a few. Some of the most important bits of info are the 16 different 'what-if' risk scenarios that look at what happens to the risk of an option with changes in the price of the underlying or in volatility.

So for your EWV4 puts, OX would be looking at the risk files published by CME (these are the pa2 files that we refer to in the PC-SPAN thread). The pa2 files are published at certain times throughout the day and are snapshots of the futures price, option price and volatility at that point in time. CME normally publishes them at 10:30am, 11:30am, 4pm and then the closing pa2 around 7pm.

It looks like OX grabs the pa2 files from CME shortly after they are published and plug them into their system. When you look at your balances page it will calculate the futures requirements based on last pa2 file that was loaded into their system. The trade calculator is similar, but instead of using the option price from the pa2 file it appears to use the current market price. This creates the difference in the calculation that you noticed.

So, let's say you were looking at your balance page on OX around 3pm on 21 Oct, OX would have still been using the pa2 file that CME published at 11:30am for their calculations. ESZ4 had rallied an additional 10 points since that time and your puts would have had a lower value, but that would not be reflected on the balances page. The trade calculator was more accurate because it was using the market price of the option. Two hours later, CME would have published the 4pm pa2 file and the calculations on the OX balances page would have been closer to what you were seeing with the trade calculator.

That was the delay I was trying to describe. Hope this makes sense.

so I have one last question, we should look at our accumulated "Total Requirement" to manage all our positions, but this number seems always be less than the 'Future Requirement' in acct summary, sometimes, we may still have fund available as excess, but the Buying Power in the acct summary could be negative because of the delay, then what going to happen? will OX issue a margin call? anybody had any experience? Thanks!

I have a question for the margin requirement. I only have 9 EWV41500P in my OX acct, I checked the IM at OX, it shows the IM is $455.4, but the 'future requirement' is $1728 for these 9 short puts. My total acct value is $21224.44, so the fund available for me to put more position is (21224.44-1728=)19496.44, but I feel like if the $455.4 is IM for these positions, I should have (21224.44-455.4*3)=$19585.24 to use based on the 3x method used in the thread.

Q1:
The available fund to trade from OX is 19496.44 which is less than $19585.24 which is from our method, that means if I use 3x IM to put on trade and assume I use all the $19585.24, I will put myself to a margin call immediately, is that right?

Q2:
I called OX to ask why the IM is $455.4 but the item 'future requirement' is $1728, they said $1728 is SPAN requirement for these positions. Since I don't have SPAN program, can someone help to check for that? what is the SPAN for 9 EWV41500P? and also please help answer the Q1 if you understand, thanks!

sorry, PS: EWV41500P

edit: when I look at my acct now, it is something like this, and the future requirement $477.9 is more close to what was required for my 9 short put EWV41500p yesterday, but when I checked the trade calculator', the IM now is 0.00. so I have one last question, we should look at our accumulated "Total Requirement" to manage all our positions, but this number seems always be less than the 'Future Requirement' in acct summary, sometimes, we may still have fund available as excess, but the Buying Power in the acct summary could be negative because of the delay, then what going to happen? will OX issue a margin call? anybody had any experience? Thanks!

The 3X method has nothing to do with how OX calculates your Buying Power or determining if you are on margin call. So the answer to Q1 is no. They only use IM and the value of the option.

Dudetooth,

I could be wrong but I never saw OX update the SPAN IM requirements through the day. They only use the SPAN IM from the prior night. I have been checking an option today on the Trade Calculator and it has the same SPAN IM now as it had at 9 am.

When I was trading there I never saw their Buying Power or IM disagree with mine which was calculated using the prior night's numbers.

The CLF15 price at 9 am was 82.29. At 2 pm it was 80.68.

I could be wrong but I never saw OX update the SPAN IM requirements through the day. They only use the SPAN IM from the prior night. I have been checking an option today on the Trade Calculator and it has the same SPAN IM now as it had at 9 am.

When I was trading there I never saw their Buying Power or IM disagree with mine which was calculated using the prior night's numbers.