Pin risk

Pin risk is the uncertainty that arises when a stock's price is trading very close to a short option's strike price as expiration approaches. When pinned to the strike, it becomes impossible to predict whether the option will expire ITM or OTM , creating assignment uncertainty for the short option holder.

Why pinning happens: Large open interest concentrations at specific strikes create self-reinforcing market maker hedging flows. As the stock approaches a high-OI strike, market makers buy shares as calls go ITM and sell shares as puts go ITM , pushing price back and forth around the strike like a magnet.

The risk to short option sellers: If your short option expires just $0.01 ITM, you're assigned. But if you close it before expiry to avoid assignment, you may be paying to close an option that would have expired worthless with one more tick in your favor. Either way, the uncertainty creates a difficult decision.

Gap risk after assignment: If assigned on a short call at expiration and the stock gaps down overnight before settlement, you may be forced to buy shares at a higher market price to fulfill the delivery , a loss that wasn't visible at the close.

How to manage pin risk:

• Close short options with strikes near the current price before the final hour on expiration Friday
• Don't hold short options through expiration when the stock is within $1–2 of your strike
• When in doubt, pay the small cost to close , the certainty is worth it

Example: Your short call has a $200 strike. At 3:45pm on expiration Friday, the stock is at $199.95 , bouncing around $200. You face pin risk: close now for certainty, or hold and risk assignment if it closes above $200.

Related terms: OPEX, open interest, assignment, expiration date, gamma

---