This has never happened but I am curious. Suppose 4:15PM EST, on the third Friday of the month (options expiration day) arrives, and all the ES (s&p 500 emini) options expire. Suppose one has a short option ITM. Obviously, this option will be assigned. Is the assignment and reception of the underlying futures completed by 6:00 PM EST when the s&p 500 emini market opens? If so, then I should be able to close them out at that time--correct? Seems to me that to avoid any volatility, it is best to close out the assigned futures at the open (6:00PM EST) rather than wait until morning. Comments appreciated. FYI, I typically cover ITM options or just close them out before 4:15PM on expiration Friday.