Expiration, exercise, and assignment
Options don’t last forever — and what happens at the end trips up more new traders than any other topic. Three terms carry the whole story: expiration, exercise, and assignment.
Expiration
Expiration is the last day the option exists. After it, the contract is gone. Most U.S. equity options are American-style, meaning they can be exercised any time up to expiration; index options are often European-style, exercisable only at expiration. At expiration, an option is worth exactly its intrinsic value — all extrinsic value has decayed to zero.
Exercise and assignment
Exercise is the owner invoking their right — a call owner buys the shares at the strike; a put owner sells them at the strike. Assignment is the flip side: when an owner exercises, a seller of the same option is chosen (assigned) to fulfill the obligation. If you are short a call and it’s assigned, you must deliver 100 shares at the strike; short a put and assigned, you must buy 100 shares at the strike.
In practice, most in-the-money options are exercised automatically at expiration by the clearinghouse if they are in-the-money, even by just one penny. This is intended to protect owners of options who might miss or forget about expiration. However, it’s an option and an option owner can choose not to exercise an option that is in-the-money by “abandoning” it. They just need to notify their broker. While this is very rare, some sophisticated traders will abandon options that are barely in-the-money at the 3:00 p.m. CT close if the underlying moves enough between 3:00 p.m. CT and the actual end of trading 15 minutes later.
You sold a $100 put for $2 and the stock closes at $96 on expiration. The put is $4 in-the-money, so it’s exercised against you: you are assigned and must buy 100 shares at $100 ($10,000), now worth $9,600. Your net cost basis is $98 (the $100 strike minus the $2 premium you kept) — a loss of $200 on paper, and you now own the stock.
Two risks new sellers miss
Early assignment. Because American options can be exercised any time, a short ITM option can be assigned before expiration — most commonly a short call just before a stock’s ex-dividend date, when the dividend makes early exercise worthwhile for the owner. Pin risk. If the stock closes almost exactly at your strike, you may not know whether you’ll be assigned, leaving an uncertain position over the weekend.
Common pitfalls
Letting an ITM option auto-exercise by accident. A long ITM call you can’t afford to exercise, or forgot about, can land you a large unwanted stock position. Close or manage before expiration.
Selling calls through a dividend without expecting early assignment. Short ITM calls are frequently assigned the day before ex-dividend.
What to do with this
Know your expiration dates, know whether you’re American or European style, and never carry a short ITM option into expiration — or through a dividend — without a plan for assignment. With the full life cycle in hand, the last foundation is a picture that ties it all together: the payoff diagram.
Next lesson · continue the courseHow to read a payoff diagram →
Assignment and exercise mechanics get their own deep-dive in the Execution & Risk track.