When dealing with ES. What do I consider as the close value for the day? Is it price at 3:15 cst? or at 3:00 cst since thats when the US stock markets actually close?

Thanks,

The official closing price is determined by the CME at 3:15 CST (except for the last trading day of the month when they use 3:00 CST). I have never known anyone to use anything but 3:15, but if you are using data that is based on settlement prices, you will notice some differences on the last trading day of the month. CME settlement procedures are listed here End of Month Settlement Procedures.

Anyone aware of an indicator that does OR could easily be modified to plot previous day OHLC to be used in an NT8 Strategy Builder BOT?

I also use the 3:15 close, hope that helps

FWIW, I use 3:00. That's when the US stock market closes. It's a significant level in my backtesting.

Maybe 3:15 is also significant?