Risk Reversals: A Synthetic Tilt and the Skew You Pay For

Buy a call and sell a put at the same strike and expiration, and put-call parity says you own synthetic stock: the same gains and losses as the shares, give or take carry and dividends. Move the two strikes apart, the put lower and the call higher, and you get a risk reversal. It still behaves like stock when the price moves far enough, but it has a flat zone in the middle where nothing happens. It is often described as a "free" way to get exposure because the put pays for the call. It is not free. The price is set by skew, and the risk sits on the side that was sold.

The rules first

Read it as stock with a gap. Above the call strike it gains like long stock; below the put strike it loses like long stock; in between it is flat apart from the net premium.
The short put is the real position. A risk reversal can lose almost the full put strike if the underlying collapses. Size it to that, not to the small net debit or credit.
Skew sets the price. On most equity indexes, downside puts carry higher implied volatility than upside calls the same distance away. That is why the put often pays for the call, and it is also the market's way of charging for the downside you are taking on.
A net credit is not a profit. It is the premium for carrying crash risk. Count it the way an insurer counts a premium: income that comes with a liability.
The mirror image is a collar. Long stock plus a long put and a short call is long stock minus a risk reversal. Knowing one structure means knowing the other.

What it really holds

Parity ties a call, a put, the stock and financing together. At one strike, long call minus long put equals long stock minus the present value of the strike. Pull the strikes apart and that clean identity breaks into three pieces: synthetic long stock below the put strike, no exposure between the strikes, and synthetic long stock again above the call strike. Delta tells the same story in real time. Near the money, a risk reversal built from a 30-delta call and a 30-delta put has a delta of roughly 0.60, more than half a share per share of notional, before the price has moved at all.

That is why the structure is popular with traders who want direction without the full cost of the shares, and why it is used in reverse by holders who want to protect shares without paying for a put outright.

Worked example (illustrative numbers only)

Every number here is an illustrative example, not a quote. Equity options carry a 100 multiplier.

The setup. A stock trades at 100 with three months to expiration. To keep the arithmetic simple, ignore interest and dividends. The 95 put is bid at 2.94 on an implied volatility of 26%. The 105 call is offered at 2.06 on an implied volatility of 20%. The two strikes are the same distance from the price, but the put is priced on six more volatility points. That gap is the skew.

The trade. Buy the 105 call for 2.06 and sell the 95 put for 2.94. Net credit: 0.88, or $88 per pair.

At expiration:

Stock at 112: the call is worth 7.00, the put expires. Result: 7.00 plus 0.88 = 7.88, or $788.
Stock anywhere from 95 to 105: both expire. Result: the 0.88 credit, or $88.
Stock at 88: the put is worth 7.00 against you. Result: minus 7.00 plus 0.88 = minus 6.12, or $612.
Breakeven: 95 minus 0.88 = 94.12.
Worst case: if the stock goes to zero, the loss is 94.12, or $9,412 per pair. The upside is open-ended; the downside is nearly the whole put strike.

The skew in dollars. Suppose both options had been priced on the same 23% volatility. The put would have been worth about 2.41 and the call about 2.62, and the same trade would have cost a small debit of 0.21. The swing from a 0.21 debit to a 0.88 credit, about 1.09, is the skew: the market paying you to hold the downside it worries about most. Whether that payment is generous or thin depends on how steep skew is relative to its own history, not on the fact that the trade opens for a credit.

The collar mirror. A holder of 100 shares at 100 who sells the 105 call and buys the 95 put does the exact opposite trade and pays 0.88. Their shares are now bounded between 95 and 105 for three months. The 0.88 they pay includes the same skew premium, seen from the side buying protection.

When it tends to make sense

When the trader would be content to own the stock at the put strike. Assignment below 95 is the risk reversal working as designed; if owning the shares there would be unwelcome, the structure does not fit.
When skew is steep relative to its history. Selling expensive downside volatility to buy cheaper upside volatility is a relative-value view on the shape of the surface, not only a view on direction.
When the account can carry the full put-side risk. The margin on the short put, and the cash needed if assigned, should already be set aside.
As a collar, when protecting a concentrated holding and giving up the upside above the call strike is acceptable for the protection below the put.

Common mistakes

Sizing to the premium. A trade that opens for a small credit can still carry a five-figure worst case per pair. Size to the short put.
Calling it free. A zero-cost risk reversal is paid for with downside exposure, and the bill arrives in exactly the market where it hurts most.
Ignoring the skew move. In a selloff, put volatility often rises faster than call volatility. The position can lose on price and on the shape of the surface at the same time.
Forgetting dividends and early assignment. A deep in-the-money short put on a stock can be assigned before expiration, especially when the time value left is small.
Treating it as a cheap call. A long call alone risks only its premium. Adding the short put changes the risk from a known debit to the full downside below the put strike.

A short risk-reversal checklist

Write the breakeven and the worst-case loss if the underlying goes to zero.
Compare the put and call implied volatilities, and note where that skew sits against its own range.
Confirm you would accept owning the shares at the put strike, and that the cash or margin is there.
Check the calendar for earnings, dividends and events inside the expiration.
Decide in advance what you will do if the put strike is breached before expiration.

Parity, synthetic positions and reading the price of skew are covered in depth in Options Synthetics.