What happens at options expiration?

Expiration is the moment an option's life ends: the last point at which it can be exercised, after which it either turns into stock or turns into nothing. For most US equity options that moment is the close of trading on the option's expiration Friday, and what happens next depends entirely on one thing, whether the option finished in or out of the money.

Here is the part beginners miss: expiration is not always a quiet non-event. If your option is worthless it simply vanishes. But if it still has value at the bell, your broker acts for you, automatically, and you can wake up Saturday owning something you did not plan to own. Doing nothing is a decision, and sometimes an expensive one.

The numbers

You bought one $105 call on a $100 stock for $3.00, so $300 left your account. Thirty days pass and it is now 4:00pm on expiration Friday. Three things can happen, and they are not variations of the same outcome, they are three different lives:

4:00pm, expiration Friday

Drag the closing price of the stock. Same $105 call you paid $3.00 for. Watch which of the three lives you get.

$103.00
strike $105

Option is worth
Your net on the trade
If you do nothing

Where it bites

"I forgot I had it" is not a defense. An in-the-money option left open at expiry is exercised automatically. A long call turns into 100 shares you must pay for, a long put turns into 100 shares sold short. People who thought their trade "just expires" wake up to a five-figure position and a Monday margin call.

Pin risk is real. When the stock closes a hair from the strike, whether you get exercised is a coin flip decided after hours. If you sold the option, this is assignment roulette. Do not hold to the bell hoping, close it.

Out of the money, it is the finish line for time value. Everything theta was eating all month arrives here: at expiry, time value is exactly zero. An option that is not in the money is worth nothing, no matter how close it got.

Go feel it

The cleanest way to understand expiration is to watch one arrive. Hold a call to the last day with play money and see it either melt to zero or snap into stock, in Lesson 4: The Clock Is Always Running. And before you ever sell an option that could be exercised against you, walk through The Premium Trap.

Related concepts: theta decay · assignment · ITM, OTM, ATM