The amount paid by the customer when using a broker's credit to buy or sell a security. Under Federal Reserve regulations, the initial margin required since 1934 has ranged from 40 percent up to 100 percent of the purchase price. Since 1974, the current rate of 50 percent has been in effect.
A demand upon a customer to put up money or securities with the broker. The call is made when a purchase is made or if a customer's equity in a margin account declines below a minimum standard set by the exchange or by the firm.