Margin Calls Explained

Borrowing money to invest can amplify gains, and a margin call is the moment that same leverage turns against you, forcing a decision under time pressure.

How margin accounts work

A margin account lets an investor borrow money from their broker, using existing securities as collateral, to buy more than they could with cash alone. This leverage magnifies both gains and losses: a portfolio bought half with borrowed money moves twice as fast, in either direction, as the same portfolio bought outright. In exchange for the loan, brokers require the account to maintain a minimum level of equity relative to the size of the position at all times.

Maintenance margin and when a call is triggered

That minimum is called the maintenance margin requirement, typically set somewhere around 25% to 30% of the position's value, though brokers can and do set higher thresholds for volatile securities. If the value of the securities in the account falls enough that the investor's equity drops below that threshold, the broker issues a margin call, demanding the investor deposit additional cash or securities to bring the account back into compliance, usually within a short window.

What happens when the call isn't met

If the investor can't or doesn't meet the call in time, the broker has the right to sell, or liquidate, positions in the account without further consent, in whatever amount needed to restore the required equity level. This liquidation typically happens at the broker's discretion and at prevailing market prices, which can mean selling into a falling market at an unfavorable moment, locking in losses the investor might have preferred to ride out.

Why margin calls amplify market declines

Forced liquidation doesn't just affect the individual investor. At scale, it can affect the broader market. When prices fall sharply, margin calls often hit many leveraged accounts simultaneously, and the resulting wave of forced selling adds extra supply into an already declining market, pushing prices down further and triggering yet more margin calls in a self-reinforcing spiral. This dynamic has been cited as an amplifying factor in several historical market downturns, which is why risk-conscious investors typically use leverage cautiously, keep a buffer well above the maintenance requirement, and understand in advance how much of a price decline their account can absorb before a call is triggered. Because the broker's liquidation, not the investor's own judgment, decides what gets sold and when, margin calls can force an exit from a position at precisely the worst possible moment.