Synthetic Short
A synthetic short was an options position constructed by simultaneously selling a call option and buying a put option at the same strike and expiry on the same underlying, replicating the payoff of being short the underlying asset without actually shorting shares or selling a futures contract.
The synthetic short was the mirror image of the synthetic long. By combining a long put and a short call at the same strike and expiry, a trader created a position whose profit-and-loss profile tracked a short position in the underlying with near-perfect fidelity, as dictated by put-call parity. As the underlying price fell, the long put gained intrinsic value while the short call lost value, producing a net gain equivalent to being short the asset. As the underlying rose, the reverse occurred.
In Indian markets, the synthetic short had a particularly relevant application in the context of shorting restrictions on equities. While short-selling of Indian shares in the cash segment was permitted intraday, overnight short positions in cash stocks were not allowed for retail participants. Futures contracts solved this problem for liquid stocks in the F&O segment, but for traders who preferred options — perhaps to gain a volatility edge or manage capital differently — the synthetic short provided equivalent exposure for the duration of the chosen expiry.
The capital requirement for maintaining a synthetic short centred on the naked short call leg. The long put, being a paid-for option, required no ongoing margin beyond its premium cost, but the short call required SPAN margin as it represented unlimited upside risk. If the stock rallied sharply, the short call loss could substantially exceed the premium collected, and the long put's gains would not fully offset unless the put had intrinsic value — which it would not if the stock was above the shared strike.
Synthetic shorts were also used by sophisticated arbitrageurs to exploit mispricings between the futures and options markets. If the implied forward price from the synthetic (derived from the options strikes and net premium) differed materially from the actual futures price after accounting for transaction costs, an arbitrage involving the synthetic short paired with a long futures position — or a synthetic long paired with a short futures — was theoretically risk-free.
An important consideration in India's physical settlement framework for single-stock options (introduced by SEBI in 2019) was the risk of delivery obligations. A short call that ended in-the-money at expiry on a stock option could result in delivery obligations. Traders using synthetic short positions on individual stocks were required to understand and plan for the settlement mechanics to avoid unintended delivery-related complications or margin shortfalls at expiry.