What Is the Difference between a “Closing Auction” and a “Settlement Window”?

A closing auction is a specific, short period at the end of a trading day where all market orders and remaining limit orders are executed simultaneously at a single price to determine the closing price. A settlement window is a longer, defined period (e.g.

30-60 minutes) leading up to expiration, during which prices are sampled and averaged to calculate the final cash settlement price. The closing auction is a price-discovery mechanism, while the settlement window is a price-averaging mechanism.