The vast majority of people who buy and sell securities in the stock exchange cannot directly participate in the transaction, but entrust brokers with membership. Every operation, investors should provide information such as varieties and prices to the securities company. This is called placing an order, and the securities company will complete the operation on your behalf according to your order information.
The advantage of paying the bill in advance is that you can lay out the buying points and selling points in advance to get ahead of others, but only if you have good trend judgment ability.
Note: the function of paying the bill in advance is provided by the brokerage firm (your agent), and the specific function and operation time are of course determined by it, which has nothing to do with the exchanges (such as Shanghai Stock Exchange and Shenzhen Stock Exchange). The bill finally submitted to the exchange is still at the official trading time.
An example of application: some stocks that may have a daily limit as soon as they open, and submit the prepaid purchase order in advance, can avoid the trouble that they can't buy because they have a daily limit as soon as they open. Similarly, for stocks that may fall as soon as they open, submitting the prepaid bill for sale in advance can also improve your chances of escape.
Application example 2: If you have a clear grasp of the trend of the stock price, but have no time to operate when the market opens, you can also submit a prepaid bill before the market opens (even the night before), and then you can "automatically" trade after the market opens.
Application Example 3: Prepaid bills generally let you directly divide orders into different numbers. When the market has opened, it is more convenient to use this function to lighten or add positions in batches. For big money speculators, it can improve the efficiency of "work" and facilitate those who like to hide big orders.