Put-Call Parity Arbitrage

Put call parity says a call and a put at the same strike and expiration must price in a fixed relationship to the underlying and the discounted strike. This sheet computes both sides of that identity from current option asks and the stock's last price, so a gap wide enough to survive spreads and financing costs shows up as a number rather than a hunch.

Strike and expiration inputs generate the option symbols and the quotes are pulled on demand. Apparent gaps usually close once bid ask spreads, dividends and early exercise on American options are accounted for.