What Is a Margin Call? | How Do Futures Work?

A margin call is a demand from your broker to deposit more money because losses have pushed your futures account below the maintenance margin level. In futures, you generally have to bring the account back up to the initial margin level, not just to maintenance.

The two levels

Initial margin: the deposit required to open a position. Exchanges call it a performance bond, not a down payment.
Maintenance margin: a lower floor. If your account equity falls below it, a margin call is triggered.

Exchanges set minimum levels and change them as volatility changes. Brokers can and often do require more than the exchange minimum. See how futures margin works.

A worked example

Margin figures and prices are illustrative, not current requirements. You buy one WTI crude oil contract (1,000 barrels) at $70.00. Suppose initial margin is $6,000 and maintenance is $5,500, and you deposit exactly $6,000.

Day	Settlement	Daily P&L	Account equity
Day 1	$69.80	-$200	$5,800
Day 2	$69.30	-$500	$5,300

At $5,300, equity is below the $5,500 maintenance level. You get a margin call for:

$6,000 - $5,300 = $700

The call is to restore initial margin ($6,000), not maintenance ($5,500). Each $0.01 move is $10 on this contract, so a 70-cent drop over two days cost $700.

What you can do

Deposit the money by the broker’s deadline.
Reduce or close the position so the remaining positions fit within your equity.

What you generally cannot do is wait. Futures are marked to market daily, so losses are settled in cash every day.

What happens if you don’t meet it

Your account agreement almost always gives the broker the right to liquidate your positions without asking, at whatever price the market offers. Many retail brokers also run automatic liquidation when intraday losses cross a threshold, before the end-of-day call. If the market gaps and the liquidation price is worse than your account balance can cover, you are left with a debit balance, and you still owe it.

Why margin calls can come suddenly

Leverage. A small percentage move in the underlying can be a large percentage of your margin. See leverage.
Margin hikes. Exchanges can raise margin requirements in volatile markets. A higher maintenance level can trigger calls even if prices have not moved.
Gaps. Prices can jump overnight or on news, past any stop order.
Limit moves. In contracts with daily price limits, you may not be able to exit at all while the market is locked. See limit moves and circuit breakers.

In short

A margin call is not a penalty. It is the system working as designed, making sure losses are covered before they grow. The risk is that it arrives when prices are moving fastest, and the broker can close you out if you cannot pay.