Customer number (also called "customer number") is a 12 digit number set for you when you open an account. The first four digits are generally the branch code of the sales department, and the last eight digits are your serial number in the sales department. Under the customer number, you can link the securities accounts and open-end fund accounts of various fund companies. You need to enter the customer number when logging in to the trading software. If the customer number is 13 digits, you only need to enter the first 12 digits when logging in the software.