Home › Academy › Options from zero to confident

Intermediate · Lesson 4 of 6

American vs European, exercise and assignment

6 minute read · By Krishna Avadhani, Vestora Academy · Updated 18 October 2026

American-style options can be exercised any time before expiry; European-style only at expiry. Most single-stock options on the ASX and in the US are American-style. Index options such as ASX XJO and S&P 500 SPX options are European-style and cash-settled.

When a buyer exercises, a writer is assigned at random through the clearing house and must deliver (call) or buy (put) the shares at the strike. Early exercise of calls is most likely just before an ex-dividend date when the dividend exceeds the remaining time value.

The clearing house (ASX Clear, or the OCC in the US) stands between buyer and seller, so you do not depend on the other party paying. Writers must lodge margin for that reason.

Key takeaways

  • American = any time; European = at expiry only.
  • Writers can be assigned, especially before ex-dividend dates.
  • Clearing houses guarantee performance; writers post margin.

Check your understanding

1. Which is usually European-style?

  • ASX BHP options
  • US Apple options
  • ASX XJO index options
  • All options
Show the answer

ASX XJO index options. Index options like XJO and SPX are European and cash-settled.

2. When is early exercise of a call most likely?

  • Right after listing
  • Just before an ex-dividend date
  • When volatility rises
  • Never
Show the answer

Just before an ex-dividend date. Holders exercise to capture the dividend.

Go deeper

Practise this in Vestora

Look up real shares, test ideas with paper trading, and track your progress through the course.

Open the app free

General education only, not financial advice. Examples are illustrations. Rules, tax settings and products change; check official sources.