In Forex trading, a margin call is a situation where a broker requires a trader to deposit additional funds into their trading account to meet the minimum margin requirement.
This happens when the trader's margin level drops below a certain value - account equity (the current value of the account including profit and loss on open positions) falls below a certain percentage of the used margin (the amount of money locked up as collateral for those open positions).
When a margin call occurs, the broker will typically notify the trader that they will soon need to increase their available margin.
This can be done in a few ways, a trader can deposit additional funds into the account, close open positions, or hope that open positions will move less into loss or into profit to bring their account equity back above the required margin level.
If the trader fails to increase their equity within a specified time, or before their margin level reaches a specific level, the broker may start closing out some or all of the trader's positions (known as "margin liquidation" or "broker stop-out") to prevent further losses that the traders account cannot cover.
VEMA aims to prevent users receiving margin calls by notifying a trader if a position being set up would cause their margin level to drop below 200%, and by sending an email when margin level drops below 140%.
Note: It's important to understand different brokers have different margin level requirements for both Margin Calls and Broker Stop outs. Make sure to understand your brokers levels to best avoid facing margin calls and stop outs.