A firm will do that if you trade "too many" other markets at the same time and are at risk of being filled on too many other initiating orders at the same time thereby leaving you undermargined and subject to a margin call.Quote from Shagi:
----If you place a limit order, they would deduct the margin from equity before order was even filled....

Quote from nazzdack:
A firm will do that if you trade "too many" other markets at the same time and are at risk of being filled on too many other initiating orders at the same time thereby leaving you undermargined and subject to a margin call.![]()