Overnight Margin
Overnight margin is the full margin requirement set by the CME that applies to futures positions held past the end of the regular trading session. It is substantially higher than intraday margin and reflects the full risk of holding a leveraged position through market-closed hours.
Overnight margin is the minimum capital required to hold a futures position through the overnight session: from the regular session close until the next day’s open. It is calculated using the CME’s SPAN (Standard Portfolio Analysis of Risk) margining system and is updated daily based on recent volatility.
Overnight vs intraday margin
| Intraday margin | Overnight margin | |
|---|---|---|
| Set by | Broker / prop firm | CME (SPAN) |
| When it applies | During regular session | After session close |
| Typical ES | $500 – $1,500 | $12,000 – $15,000 |
| Typical MES | $50 – $150 | $1,200 – $1,500 |
Overnight margin for ES is typically 10–20× higher than intraday margin. This reflects the risk of holding through earnings, economic releases, and geopolitical events that can cause large overnight gaps.
SPAN margining
SPAN calculates margin by simulating how a portfolio would perform across 16 risk scenarios: different combinations of price moves and volatility changes. The worst-case loss across those scenarios determines the margin requirement.
SPAN margin updates daily (sometimes intraday during high-volatility periods) and is passed to brokers as the minimum they must charge customers. Brokers may add additional cushion on top.
Who holds overnight
Most retail day traders and prop firm traders do not hold positions overnight. The primary reasons:
- Cost: overnight margin ties up much more capital
- Risk: gaps on economic releases (CPI, NFP, Fed decisions) can move ES 50–100+ points in seconds
- Prop firm rules: most funded accounts prohibit overnight holding entirely
Swing traders and institutional traders who have the capital and risk appetite do hold overnight, accepting the gap risk as part of their strategy.
Practical implication for day traders
Even if you intend to close before the end of session, understand what your overnight margin requirement is. If you accidentally hold past the cutoff: due to a platform issue, connectivity problem, or simple oversight: your account needs sufficient capital to meet the overnight requirement or your broker will auto-liquidate your position.