Short Call

The position is one leg, but because you are selling, the exchange requires margin to be posted before entry.

Enter with a sell to open order and confirm the margin requirement before placing it. Margin on short index options runs far larger than the premium collected, so the return on capital is smaller than the raw premium suggests.

Most sellers do not hold to the last day. A common practice is buying the call back once most of its value has decayed, for example at 10 to 20 percent of the entry premium, because the last few points of profit are not worth days of open ended risk.

Have a hard exit rule for the wrong direction, whether that is a fixed multiple of the premium (many sellers cut at 2x) or a level on the index. Hoping a runaway rally reverses is how small income trades become account defining losses.

Theta is the engine of this trade. The premium you sold contains time value that evaporates day by day and lands in your pocket, fastest in the final two to three weeks of the contract.

This is why short call sellers usually operate in near dated expiries and simply repeat the process, rather than selling long dated options where decay trickles rather than flows.

A short call is short vega: falling implied volatility shrinks the option's value and hands you profit even in a motionless market. Selling when IV is unusually high, and letting the eventual normalisation do part of the work, is the classic edge sellers hunt for.

The reverse is the risk. A volatility spike inflates the call you are short, produces mark to market losses before the index has even moved much, and can trigger higher margin requirements at the worst time.

The cleanest defence is converting to a bear call spread: buy a higher strike call against your short. This caps the maximum loss at the strike difference minus the net credit, in exchange for a small cost.

If the index grinds toward your strike, rolling up and out, buying back the current call and selling a higher strike in a later expiry, collects more premium and moves the breakeven higher. Roll only when the new trade would make sense on its own.

Consider starting as a spread instead of adjusting into one. Most of the premium, a defined worst case, and calmer margins are usually worth giving up a few points of credit.

A naked short call is the opposite side of a long call. Its open ended risk is most often contained by holding the underlying against it, which turns it into a covered call.

Selling a call is also a component of many credit structures, such as the bear call spread, where a further out long call is added to cap the risk.