A margin call is a demand from a securities broker to a customer requiring the customer to deposit additional money or securities so that the margin account is brought up to the minimum maintenance margin. This occurs when the account value depreciates substantially below the broker’s required amount and can signal risk of default on loans used to purchase securities. It is essentially a safeguard by the broker to ensure that any credit extended to the customer is adequately collateralized. Margin calls can also be made as a result of excessive trading activity or market volatility, forcing traders to put up extra capital for their transactions.