Margin Calls and Forced Liquidation

Borrowed money has a feature cash doesn't: someone else can decide when you're out of the trade. A leveraged position is fine as long as its value stays above a threshold the lender sets. The moment it doesn't, the lender doesn't ask politely — it demands cash immediately, and if the cash doesn't show up, it sells your position without waiting for your opinion on the price.

The mechanics

A broker requires you to maintain equity — the value of your position minus what you owe — above a maintenance margin level, usually expressed as a percentage of the position's value. If your account's equity falls below that line, you get a margin call: post more cash or securities by a deadline, typically the same day or next morning.

If you don't meet the call, the broker executes a forced liquidation: it sells enough of your position, without further permission, to bring your equity back above the line. This is not a courtesy step, it is the mechanism that lets the broker safely lend you money in the first place. See Initial Margin vs Variation Margin for how the deposit that funds this buffer is set in the first place.

Worked example

You buy $20,000 of stock using $10,000 of your own cash and $10,000 borrowed (2x leverage). Maintenance margin is 25% of position value, meaning your equity must stay above 25% of whatever the position is worth.

• Position value falls to $14,000. You still owe $10,000, so equity is $4,000. Required equity is $0.25 \times 14{,}000 = 3{,}500$ ($3,500). You're still above the line, no call yet.
• Position value falls to $12,500. Equity is $2,500. Required equity is $0.25 \times 12{,}500 = 3{,}125$ ($3,125). Now you're short $625 — a margin call for at least that much.
• You don't post the $625 by the deadline. The broker sells stock to restore the ratio. Selling $X of stock reduces both the position value and, since the loan stays at $10,000 until repaid from proceeds, brings equity back to the required 25% line. Working through the algebra, the broker needs to sell roughly $2,500 of stock to get the account back into compliance.

Notice the position was liquidated at the bottom of a decline, exactly when the price is worst — the call is triggered by weakness, and the sale adds more selling into that weakness.

Why liquidations cluster and cascade

Forced liquidation rarely happens to one account in isolation. A market-wide price drop pushes many leveraged accounts below their maintenance lines at once, since they're all long the same falling asset. Each broker's forced selling adds supply into an already-weak market, pushing the price down further, which triggers the next wave of margin calls on accounts that were previously fine. This feedback loop is a core mechanism behind sharp, fast crashes — the 2021 Archegos collapse and repeated crypto "liquidation cascades" both follow this exact pattern, just with different collateral and different brokers on the other side.

What this means in practice

• Leverage compounds badly on the way down, not just because losses are amplified, but because the forced exit happens exactly when you'd least want to sell. A cash account never forces you out at the bottom; a margin account can.
• Correlated positions are more dangerous than they look, because a single adverse move can trigger simultaneous calls across everything you hold, leaving no unencumbered asset to post as new collateral. See Funding Liquidity Risk.
• Some traders hedge specifically against this scenario — holding an out-of-the-money option or futures position whose payoff shows up exactly when a liquidation would otherwise be forced. See Tail-Risk Hedging.