You can refer to the delivery rules of Dalian Commodity Exchange:
Article 19 The first day of the rolling delivery process is the pairing day.
(1) The seller declares delivery. After delivery, customers who hold standard warehouse receipts (except warehouse receipts with margin, the same below) and one-way selling positions in the delivery month can apply for delivery through members, and members can declare delivery to the Exchange from the first trading day to the closing day of the last trading day in the delivery month. The corresponding positions and warehouse receipts for delivery shall be frozen, and the trading deposit corresponding to the selling positions shall not be charged.
(2) The buyer declares its intention. A buyer who holds a one-way buying position in the delivery month may declare the delivery intention to the Exchange before the market closes from the first trading day of the delivery month to the trading day before the last trading day.
Article 20 After the market closes on the matching day, the Exchange will find out the long positions in the delivery month for the seller members who apply for delivery through the system, and make delivery matching according to the principle of "the position of the buyer who declares the intention of delivery takes precedence, and the position of the buyer who holds the position for the longest time takes precedence". Once the matching result is confirmed, the buyer and the seller shall not change it.