There is no “end of day” only requirement on margin calls. A brokerage firm could margin call you 2min after the market opened, as an example. The trigger is wh

There is no “end of day” only requirement on margin calls. A brokerage firm could margin call you 2min after the market opened, as an example. The trigger is when your account is out of balance with the established risks the brokerage is willing to extend to you, which they can change the criteria at will. More details on margin calls here: https://www.thebalance.com/what-is-margin-call-358106 https://www.thebalance.com/what-is-margin-call-358106