Margin calls and auto-liquidation

In the movies a margin call is a phone call from a broker. In a modern retail futures account it is an automated process that closes your position at market, charges you a fee and sends an email afterwards. Understanding exactly when it triggers, and what the broker's algorithm does when it triggers, is the difference between a planned loss and a much worse one.

The overnight margin call

At the end of each day, your broker computes:

equity = cash + realized P&L + unrealized P&L on open positions

and compares it to the total maintenance margin on everything you hold. If equity is below maintenance, you are on call. The rules from there vary by broker but the usual shape is:

1. You are notified, and given until a stated time (often before the next session's open, sometimes the same day) to deposit funds to bring equity back up to initial margin.
2. If you do not, the broker liquidates enough positions to bring you back into compliance, or everything, at its discretion.
3. A liquidation fee is charged per contract, commonly in the range of $25 to $50.

Worked example. You hold 2 MES overnight. Initial $1,600 each, maintenance $1,450 each. Account equity at yesterday's close: $3,500, above the $3,200 initial. Overnight the index falls 1.5%, 75 points. Unrealized loss = 75 × $5 × 2 = $750. Equity = $2,750. Maintenance for 2 contracts = $2,900. You are on call for $3,200 − $2,750 = $450 (back to initial). Deposit it or one contract goes.

The arithmetic to know is how far the market has to move to put you on call:

points to call = (equity − total maintenance) ÷ (contracts × point value)

For the example: (3,500 − 2,900) ÷ (2 × 5) = 60 points, or 1.2% on the index. That is the buffer you actually had. Most people on this trade thought they had $3,500 of buffer.

Intraday auto-liquidation

Day-trade margins work because the broker's risk engine watches every account in real time. The typical rule is a liquidation threshold expressed either as a fixed dollar amount of equity or as a percentage of the day-trade margin posted. If your equity falls to the threshold, the engine sends market orders to flatten you. There is no call and no grace period; the email arrives after the fact.

Suppose the broker's rule is "liquidate when equity falls below 100% of day-trade margin held" and you have $1,200 in the account, long 1 ES on $500 day-trade margin. Equity can fall $700 before liquidation, which is 14 ES points. The S&P moves 14 points in a quiet ten minutes. You did not choose a 14-point stop; the broker chose it for you, and it will be executed at market with a fee.

The MES rows have enormous buffers because the position is small relative to the account. In those rows, your own stop is the binding constraint, as it should be. In the ES rows, the broker's liquidation level is close enough to be a real risk of firing before your stop does.

What the algorithm does, and why it is worse than your stop

Three features of forced liquidation make it more expensive than a stop you placed yourself:

• It is always a market order, often at a moment when the market is moving fast, because that is what triggered it.
• It closes everything, not just the losing position. If you hold a winning position elsewhere, that goes too.
• It charges a fee, and some brokers restrict the account afterwards.

There is also a subtler cost: liquidation happens at the broker's threshold, which is unrelated to any level on your chart. A trade that would have worked with a 20-point stop gets closed at 14 because the account was too small to hold the contract, and the trader records it as a losing trade rather than as a sizing error.

Key idea: A margin call is triggered when equity falls below maintenance; auto-liquidation is triggered by the broker's real-time threshold. Compute the distance to each in points before you enter. If it is close to your stop, the position is too big.

Negative balances

Futures accounts can go negative. If a gap or a limit move (Module 5) takes equity below zero, you owe the broker the difference, and they will pursue it. Cash-settled index futures held overnight through a crash, and physically delivered contracts held into an event, are the two classic routes. Neither happens to a trader who keeps account leverage low and is flat before events they cannot size for.

Try it: Find your broker's written liquidation policy: the intraday threshold, the overnight call deadline, the fee per contract, and whether they liquidate the losing position only or the whole account. Then, for a position you might hold, compute the points-to-call and points-to-liquidation using the formulas above and compare them to your planned stop.

Recap

• Margin call: equity below maintenance at settlement; you must restore to initial or be liquidated, with a fee.
• points to call = (equity − maintenance) ÷ (contracts × point value); most traders overestimate this buffer.
• Intraday auto-liquidation triggers at a broker threshold with no grace period, at market, and often flattens everything.
• If the broker's liquidation level is near your planned stop, the position is too large for the account.
• Futures accounts can go negative; low account leverage and being flat for events prevent it.