ES options are not cash settled! ES futures are cash settled, but the options expire into an ES futures position if the option is in the money. For example if you had 1 itm weekly call option today you would end up buying one ES contract at the call price which you would now own over the weekend. Warning here, the margin for one ES contract is substantially higher than for your call option. Double warning, IB will look at your ES option positions up to 2 days before expiration and if they think you may expire itm and you don't have margin to buy/sell the underlying ES they'll start auto liquidating your account, no warning. Even if the option then expires worthless. The criteria they use to determine if your option will expire itm is a secret, customer service will just blame "the algorithm" that seems to run IB. I had a bunch of 5 point ES spreads auto liquidated this way, never traded ES with IB again.