A demand from a broker for an investor to deposit additional funds or securities to bring a margin account back up to the required minimum maintenance level.
Margin calls occur when the value of securities in a margin account falls below the broker's required maintenance margin. If you fail to meet a margin call, the broker can liquidate your positions without notice, potentially at the worst possible time and at unfavorable prices. During the March 2020 COVID crash, margin calls accelerated selling across the market. To avoid margin calls, experienced investors maintain a buffer above the maintenance requirement, use stop-loss orders to limit position losses, and avoid concentrating margin in volatile securities. Margin calls have been responsible for some of the most dramatic losses in trading history.