Basics

Option exercise

Not every option is exercised in the same way. The key variables are exercise style, underlying type, and whether expiry leads to stock delivery or cash settlement.

Exercise Style

American or European

The first distinction is between American and European exercise style. American style means the holder of a long option may generally exercise before expiration. European style means exercise is only possible at expiration.

That is why stock and ETF options can create early exercise and early assignment risk. If you are short an American-style contract, assignment can happen before the last trading day.

Simple rule of thumb

  • American style Long holder may exercise before expiry.
  • European style Exercise only happens at expiration or settlement.
  • Practice Many single-stock and ETF options are physically settled, while major index options are often cash-settled.

What happens with stock and ETF options

For standard stock and ETF options, exercise generally leads to physical delivery. That means 100 shares per contract are booked into or out of the account. If an equity option expires in the money, OCC processing will typically exercise it by exception unless contrary instructions are submitted.

  • Long call ITM at expiry 100 shares are bought at the strike and booked into the account.
  • Short call ITM at expiry 100 shares are called away or must be delivered.
  • Long put ITM at expiry 100 shares are sold at the strike; depending on broker rules, this may require shares on hand or may create a short stock position.
  • Short put ITM at expiry 100 shares are booked into the account at the strike.

Practically, you should always keep enough buying power or margin in the account to support a potential stock delivery of 100 shares. That is especially true for long calls that may be auto-exercised and short puts that may result in stock assignment.

Simple stock example

  • Stock at 186 USD at expiration.
  • Long call strike 180 is 6 USD in the money.
  • Result If exercised automatically, you buy 100 shares at 180 USD.
  • Capital need Roughly 18,000 USD plus costs must be supportable by the account.

Cash settlement in index options

With many large index options such as SPX, NDX, or DAX, there is no stock delivery. Instead, only the cash amount by which the option finishes in the money is exchanged. That is called cash settlement.

The important detail is precision: settlement is based on the official settlement value of the product, not just any random last tick. Depending on the contract, that final value can be based on opening or closing prices.

Simple SPX example

  • SPX call strike 5000.
  • Official settlement value 5035.
  • Intrinsic value 35 points.
  • Cash settlement 35 x 100 = 3,500 USD.
  • Result No shares move. Only cash is credited or debited.