Two requirements for the same contract
Overnight margin is the exchange's initial requirement. It applies from the close and it is the real number.
Day margin is a discount your broker offers while the session is open — often a few hundred dollars against a five-figure overnight figure. It is not an exchange rule, it varies between brokers, and it can be withdrawn.
A typical gap on ES is around $500 intraday against $14,300 overnight — roughly 28 times. The same contract, the same day, two entirely different capital requirements.
The failure this page exists for
An account with $10,000 can hold twenty ES contracts intraday and zero overnight.
If that position is still open as the session ends, the broker closes it. Automatically, at the market, at a time it chooses. Not at your stop, not at your target, and with no regard for whether the trade was working.
The important part: this is a deadline, not a price event. Every other risk in trading arrives because the market moved. This one arrives because the clock reached a particular time while you held more than the overnight requirement. Being right about direction offers no protection at all, and the liquidation frequently happens in the thinnest liquidity of the day.
That is why the main output here is a yes or a no rather than a number.
What to check before the trade, not during
Three things, and all three are knowable in advance:
- Your broker's cut-off time. It is usually 15 to 30 minutes before the session close, not at the close itself. The window is shorter than people assume.
- Which contracts are eligible. Day margin discounts often apply only to the majors and only during specific hours.
- What happens on a holiday or an early close. Shortened sessions bring the cut-off forward, and this is where it catches even experienced traders.
If the plan is to hold overnight, size the position against the overnight requirement from the start. Sizing against the day figure and hoping to be flat by the close means every trade carries a hidden exit condition.
Why the discount exists
Not generosity. A broker offering day margin can liquidate the position while the market is open and liquid, so its own risk is small. Once the session closes, the next opportunity to exit may be a gap, and the exchange requirement is set to survive one.
This also explains why day margin disappears exactly when it would be most useful: brokers withdraw or raise it in volatile conditions, and they do so on positions already open.