Depends on the broker, but there's a secret way around it.
Say you have 50 open calls on UPST that expire that afternoon..... ie $1.5M dollars.
Your broker's system is gonna flag that and an actual human will close the position with a market order, the actual time depending on how busy they are. It could be as early as 2pm. You can always call them and tell them you're aware and watching, and that you will close by the end of the day. Some will let you do that if you have a long term relationship.
But the ultra top-secret, super sneaky trick to NOT get flagged by their computers...
I probably shouldn't write this lol.... because I'm sure at a minimum IB will fix the glitch when they read VZ's post here....
But if you want to get around a forced closing of an open option position that the acount does not have the overnight buying power to purchase the underlying on opex....
.... place a sell to close market order, but check the "market on close" box.
It trick-f's their systems lol, your position will never trigger an alert.
Just make sure you're watching.... and you better have a back-up plan if your internet goes down at 3:59:30 on Friday afternoon.
It could happen. Believe me....