Theta Decay

Zero days to expiration (0DTE) options have become one of the most actively traded instruments in the modern market. On a typical trading day, 0DTE SPX options account for more than 40–50% of all SPX options volume. The reason is simple: the theta decay is at its most powerful, the mechanics are well-defined, and for systematic sellers, the daily reset provides a clean, repeatable trading cycle. This guide covers everything you need to know to understand, evaluate, and trade 0DTE options — especially the iron condor approach on SPX. ...

Every day that passes, options lose value. For buyers, this is the silent killer of their positions. For sellers, it is a reliable, day-by-day income stream. Understanding why option selling has a structural edge — and how to harness it — is the foundation of serious, systematic options trading. The Fundamental Asymmetry Options are priced to include a premium for uncertainty — what the market calls implied volatility (IV). Historically, options tend to be overpriced relative to the actual movement that occurs. This gap between implied and realised volatility is known as the volatility risk premium (VRP) — and it consistently flows from buyers to sellers. ...