Exercise & Assignment

Exercise is the act of an option buyer using their right to buy (call) or sell (put) the underlying stock at the strike price. Assignment is the other side — it is when an option seller is obligated to fulfill that transaction. When a buyer exercises, a seller gets assigned.

Why It Matters

Most options traders never exercise or get assigned — they close positions before expiration. But understanding the mechanics is essential because automatic exercise at expiration can catch you off guard. If you hold an ITM option at expiration and don't close it, you will end up with a stock position you may not want and may not have the capital to support.

For sellers, assignment risk is always present, especially with American-style options (which can be exercised at any time before expiration). Early assignment is most common with deep ITM calls just before an ex-dividend date.

How It Works

Exercise (buyer's action):

• A call buyer exercises to buy 100 shares at the strike price
• A put buyer exercises to sell 100 shares at the strike price
• Early exercise is possible with American-style options (most equity options) at any time
• European-style options (like SPX index options) can only be exercised at expiration

Assignment (seller's obligation):

• A call seller who is assigned must sell 100 shares at the strike price
• A put seller who is assigned must buy 100 shares at the strike price
• Assignment is random — when any buyer exercises, the OCC randomly selects a seller with a matching short position

Automatic exercise at expiration: The Options Clearing Corporation (OCC) automatically exercises any option that is $0.01 or more in the money at expiration. You can instruct your broker not to exercise (called a "do not exercise" request), but you must do this before the deadline.

When early assignment happens: Early assignment is uncommon but not rare. It typically occurs when:

1. A call option is deep ITM and the stock is about to go ex-dividend
2. The extrinsic value of the option is very small (less than the dividend)
3. A put option is deep ITM and has virtually no extrinsic value remaining

Quick Example

You sold one $50 put on stock MNO for $2.00. At expiration, MNO is at $47. Your put is $3 ITM and will be automatically exercised. You are assigned: you must buy 100 shares at $50 ($5,000 total). Your effective cost basis is $48 (strike minus premium received). Since the stock is at $47, you are sitting on a $100 unrealized loss, but you kept the $200 premium.