The Margin Call in The Forex Market

A forex broker will close your open position(s) immediately if the equity in your trading account drops below the margin requirement. This to prevent you from negative account balances.

For example:

Assume you have a trading account with $20,000 and margin requirement is set to 100:1. Without any open positions, your usable margin is $20,000.

Getting a margin call scenario:

You use $15,000 to buy 15 lots of EUR/USD, you now have $5,000 of usable margin left. This means that you are allowed to lose $5,000 on the open postion before you are under the margin requirement.