In TD Ameritrade, margin accounts show a maintenance requirement for the account even if no loan was used to purchase any of the securities. Why is this? How could a margin call ever happen if no margin was used?
Also, even with cash in the account that would cover a stock purchase, a given order registers a margin balance before the trade closes. Does the broker use margin as a way to quickly fulfill an order and then settle with cash at a later time? Does this trigger the need to calculate a maintenance requirement for the entire account?