Synthetic Put

A synthetic put is a combination of two positions that behaves, in terms of risk and payoff, like an ordinary put option, even though no put is actually bought. You build it by shorting the stock (selling borrowed shares now, with the plan to buy them back later) and simultaneously buying a call option on that same stock.

The logic is about how the pieces offset each other. Short stock makes money as the price falls and loses money as it rises, with no cap on the potential loss if the price keeps climbing. The long call caps that upside loss, because it gives you the right to buy the stock back at a fixed strike price no matter how high it goes. What is left, once you combine the unlimited-loss short position with the loss-capping call, is a position that profits from a price decline but has a defined, limited loss if the stock instead rises — which is exactly the shape of a regular long put's payoff.

People build synthetic positions like this for a few reasons: the specific put strike or expiry they want may not be listed or may be illiquid, the options market may be mispriced relative to the stock in a way that makes the synthetic version cheaper, or they may already be holding one of the two legs (say, an existing short) and just add the other leg to reshape the risk.

The nuance that trips people up is that "synthetic" does not mean "identical in every detail." The combined position matches the put's profit-and-loss shape and, under standard option-pricing relationships, its price behavior, but it involves margin requirements for the short stock, stock borrow costs, and dividend obligations that a plain long put does not have. Those extra costs and mechanics mean the two are equivalent in payoff logic, not in every practical cost.