Short Strangle
A short strangle sells a put at a lower strike and a call at a higher strike on the same underlying, with equal quantities, matching contract sizes, and a common expiration. The combined premium is the maximum expiration profit, attained when the underlying finishes within the strike interval. Beyond that interval, one option’s increasing payoff reduces the credit and can eventually produce a loss.
An uncovered short strangle has substantial downside risk and unlimited upside loss potential. The put creates an obligation to purchase the underlying after a decline, while the call creates an obligation to deliver it after a rise. Receiving both premiums does not remove either obligation.
Construction and example
A hypothetical example uses SPY at $750 and options with 45 days remaining. Selling one $725 put for $6.50 per share and one $775 call for $8.50 receives $15 per share. With standard 100-share contracts, the premiums are $650 and $850, for a combined credit of $1,500. The example assumes no purchased options or shares offsetting the short contracts.
Expiration payoff
From $725 through $775 at expiration, including the endpoints, neither option has intrinsic value. The entire $1,500 credit is then the maximum profit. Below the put strike, the disadvantage of purchasing at $725 grows as the market falls. Above the call strike, the disadvantage of delivering at $775 grows as the market rises.
At $720, the put has $5 per share of intrinsic value and the call has none. The $5 per-share obligation leaves a $10 per-share profit after the $15 credit, or $1,000 for the pair. At $780, the call creates the same obligation and result. In each case, one option is in the money but the position remains profitable because the obligation is smaller than the total premium received.
The credit is fully used at $710 on the downside and $790 on the upside. At either $700 or $800, one option has a $25 per-share payoff, or $2,500 per contract. Subtracting that obligation from the $15 per-share credit gives a $10 per-share loss, or $1,000 after the $1,500 contract credit.
The graph has a flat maximum between the strikes and declining results outside that interval. Beyond either break-even, every additional $1 adverse movement adds $100 to the pair’s loss. A zero underlying price bounds the put-side obligation, but no corresponding upper price boundary limits the call-side loss.
Value before expiration
Closing the strangle requires purchasing both options. If their combined price falls to $9 per share, repurchasing them costs $900 and realizes a $600 profit against the original $1,500 credit. A combined repurchase price above $15 per share realizes a loss.
With SPY between the strikes and other inputs unchanged, passing time generally reduces the options’ remaining value. Movement toward one strike can instead increase the nearer option’s value and make it more sensitive to further adverse movement. Near expiration, this negative-gamma exposure can change rapidly around the strike while relatively little value remains in the opposite option.
Higher implied volatility generally increases both repurchase prices. The two IVs may also change differently: lower-strike puts can become more expensive relative to calls during a selloff. The closing cost therefore reflects underlying-price movement, time, and the particular volatility change in each contract. Remaining inside the expiration profit interval does not ensure that an early closing trade will be profitable.
Exercise, assignment, and execution
SPY options permit early exercise. Assignment of the $725 put purchases 100 shares for $72,500. Assignment of the $775 call sells 100 shares for $77,500 and can create short stock if the shares were not held. These transactions are separate from the premiums already received.
After one assignment, the other short option remains open. Put assignment can leave long shares and the short call; call assignment can leave short shares and the short put. The account must support the resulting shares and remaining obligation. Collateral requirements can increase during a large market movement, and a funding deficiency may lead to liquidation.
Near either strike at expiration, after-hours movement and exercise instructions can affect whether shares remain. A complex closing order can repurchase both contracts at a net limit and fixed ratio, but it removes obligations only for the quantities actually filled and not already assigned. Shares previously created by assignment require their own closing transaction.
Payoff formulas
Let denote the put and call strikes, the combined credit per share, and the final underlying price. For matched pairs and multiplier :
The two maximum functions calculate the obligations owed on the puts and calls. Within the strike interval they are both zero, leaving the full credit as profit. For a positive credit:
The lower break-even is attainable for a stock or ETF only when it is nonnegative. With , maximum downside loss is at a zero underlying price. Above the call strike, the profit and loss slope is dollars per $1 rise, so upside loss is unlimited. Both leg quantities must be scaled together to preserve the matched-pair payoff.