What Is Maintenance Margin? The Trigger Level

Maintenance margin is the minimum account balance you must keep to hold a futures position overnight. Drop below it and your broker issues a margin call, demanding you add funds or reduce the position, often within hours. It sits below initial margin, the larger deposit required to open the trade in the first place.

What is maintenance margin?

Maintenance margin is the floor. Once you're in a position, your broker checks your account equity against this number, usually at the end of each trading session, sometimes intraday if the market moves hard against you.

If your equity falls below that floor, you get a call. You either wire more cash, close part of the position, or the broker closes it for you. Brokers differ on how much grace they give you, but none of them wait indefinitely.

This number exists because futures are leveraged. You're controlling a contract worth roughly $250,000 (at 5,000 times the S&P 500 index level) with a deposit that's a small fraction of that. The exchange and your broker need a cushion so losses get covered before they turn into a shortfall nobody can collect.

Maintenance margin vs initial margin

Initial margin is what you post to open the trade. Maintenance margin is what you need to keep holding it. Initial is always the higher number, maintenance is typically 90% or so of initial, though the exact ratio is set by the exchange and can shift with volatility.

Here's the mechanism: you deposit initial margin, the trade moves against you, your equity drains. As long as equity stays above maintenance margin, nothing happens. The moment it dips below, you owe money back up to the initial margin level, not just back up to maintenance. That's a detail people miss: the call brings you back to the higher number, not the lower one.

So a small dip below maintenance can trigger a call for more than you'd expect. If maintenance is $11,500 and initial is $12,650, and your equity slips to $11,000, the call isn't for $500. It's for $1,650, enough to get you back to the initial level.

A margin call doesn't ask you to get back to the maintenance level, it asks you to get back to initial margin, which is always the higher number.

How does a margin call actually happen?

Your broker runs an end-of-day mark to market. Every open position gets valued at the settlement price, gains and losses get applied to your cash balance, and the system compares that new balance to the maintenance requirement for whatever you're holding.

If you're short, equity below maintenance, the broker typically calls or emails first. Some brokers give you until the next session to fund the account. Others, especially with retail futures accounts, will auto-liquidate a position without warning if the shortfall is large or the market is moving fast against you.

Fast markets change the math. During a sharp intraday selloff, a broker doesn't always wait for the end-of-day mark. If your account is deep underwater in real time, risk desks can close positions mid-session to protect the firm, not just you.

ES overnight margin figures

For the E-mini S&P 500 (ES), CME sets exchange minimums, and brokers often add a buffer on top. As a rough illustration, initial margin for one ES contract has recently run in the neighborhood of $12,000 to $13,000, with maintenance margin a few hundred to a couple thousand dollars lower.

Those numbers move. CME adjusts margin requirements when volatility rises or falls, sometimes with little notice, and brokers can require more than the exchange minimum. Always check current figures directly with your broker or on the CME site before sizing a position, don't rely on a number from an old article, including this one.

One overnight-specific point: many brokers require full initial margin, not a reduced day-trading margin, to hold ES positions overnight or through economic releases. If you're used to trading with a lower intraday margin rate, the jump to overnight requirements can catch you off guard on a volatile week.

Why this matters if you're running or evaluating a system

Any automated strategy that holds positions overnight lives or dies by margin math. A system that sizes positions without a hard buffer above maintenance margin is one bad night away from a forced liquidation at the worst possible price.

This is part of why Karani caps position size and enforces a daily-loss limit on the client's own AMP/Rithmic account rather than sizing purely on account balance. The goal is to keep equity well clear of maintenance margin before volatility has a chance to close the gap for you.

None of this removes risk. Futures trading can lose money, leverage cuts both ways, and a daily-loss cap only limits how much gets lost in a single session, not whether a losing session happens.