When stock index futures expire, cash delivery is used to calculate the profit and loss of buyers and sellers and transfer funds.
The cash delivery of stock index futures is determined by the clearing institution of the exchange as the delivery settlement price, and both long and short parties make profit and loss settlement and money transfer according to this delivery settlement price, thus fulfilling their performance obligations.
The settlement price of delivery is not determined by the average price of futures trading price, but calculated by the average price of stock spot index.