Long one futures contract and short a related one, so what matters is the gap between them rather than where either goes on its own. Shocks common to both legs largely cancel, which is why exchanges margin a recognised spread far more cheaply than the same two contracts held apart. That relief is also the trap: carrying the position costs little, so it is easy to hold size the differential can move against faster than it seems it should. Set both legs here and read the margin requirement next to the widening of the spread that would consume it.
Entered as a single exchange-recognized spread order rather than two separate futures trades, which is what earns the reduced margin — legging in manually gets charged the full margin on both legs until the exchange recognizes the pair. The spread's own bid/ask is usually tighter, relative to its value, than either outright leg's bid/ask, because market makers quote the differential directly rather than two independent prices. Rolling an existing calendar position is the same order type as opening a fresh spread; there is no separate "roll" ticket.
The margin relief this earns from being entered as a single spread order disappears the moment either leg is closed independently, so exiting a spread as two separate orders briefly re-exposes the full outright margin on whichever leg is still open. Many venues quote the spread's own bid/ask directly rather than requiring the two legs to be priced separately, which is usually the tighter and more reliable way to see the real cost of entering or exiting. Because leverage here is much higher per dollar of margin than an outright position, sizing by margin required rather than by notional exposure understates the risk if the spread relationship itself breaks down.
Common mistake. The common mistake is legging out of the two contracts separately during an exit, which briefly loses the margin offset and the tight combined pricing that made the spread attractive to hold as one position.
| # | Action | Instrument | Strike |
|---|---|---|---|
| 1 | Buy | ES Sep future | 5800 |
| 2 | Sell | ES Dec future | 5845 |
Computed from the same strikes and net premium as the worked example above — not a simulation, the closed-form payoff evaluated at each price.
| Spread (Sep − Dec) | P&L |
|---|---|
| -75 | -$1500.00 |
| -60 | -$750.00 |
| -45 | $0.00 |
| -30 | $750.00 |
| -15 | $1500.00 |
| 0 | $2250.00 |
| Strategy | Market view | Opened for | Legs vs. this one |
|---|---|---|---|
| Futures Calendar Spread | Term structure — non-directional | Margin | same |
| Futures Inter-Commodity Spread | Relative value — processing margin | Margin | +1 |
| Futures Outright | Directional — leveraged, linear | Margin | -1 |
| Futures Basis Trade | Arbitrage — carry capture | Margin | same |