Here is a detail you may not have noticed: when a cash-settled option expires, the price used to calculate your profit or loss is not the price at the exact second of expiry. It is the average price over a specific time window just before expiry.
This is a practical risk-control measure. It helps prevent someone from manipulating the price at the last moment to affect your P&L.
How the final price is actually determined
Different platforms and products settle cash-settled options in slightly different ways. However, most mainstream methods generally use two concepts: time-window averaging and a specific index price.
Bybit: The final settlement price for European-style cash-settled options is the average index price over the 30 minutes before expiry.
CME: The settlement price for Bitcoin futures options is the volume-weighted average price over the last 60 minutes of the expiry day.
Hypercall (on-chain options): Settlement uses a 30-minute TWAP (time-weighted average price), not the price at the exact expiry timestamp.
Gate.io: When cash-settled options expire, they settle based on the difference between the market price and the strike price. The platform's pricing rules also follow a similar average price mechanism to reduce manipulation risk.
Why use an average price instead of an instant price?
There is one core reason: anti-manipulation.
If cash settlement only used the price at the exact second of expiry, large traders could push the price sharply up or down with one big order. That would make many options become in-the-money or out-of-the-money and allow them to profit. Using an average price over a period makes manipulation too expensive to be worthwhile.
This mechanism is essentially a form of price smoothing. Hypercall's documentation also clearly states that a 30-minute TWAP prevents last-minute price manipulation.
What happens during the 30-minute or 60-minute window?
During the settlement window, such as the 30 minutes before expiry on Bybit, there is not much you can do. Options held to expiry are settled automatically by the system, so you do not need to exercise them manually.
But this window matters because it decides how much money your option will ultimately pay out. If you see sharp price moves during this time, do not overreact. The final settlement price is an average, so a single spike or drop has limited impact on the final result.
How to check the settlement result
After option expiry, go to the platform's "Order History" or "Settlement Records". Find the settlement details. You should normally see two fields: "settlement price" and "strike price". Compare the settlement price with the market price you saw before expiry. If the settlement price is closer to an average or middle value over a period, rather than an extreme point, the average price mechanism is working.
