legal ground
Article 24 of the Law of the People's Bank of China
The People's Bank of China can issue and pay treasury bonds and other government bonds to financial institutions on behalf of the financial department of the State Council.
Article 25
The People's Bank of China may open accounts for financial institutions as required, but may not overdraw the accounts of financial institutions.
Article 26
The People's Bank of China organizes or assists in organizing clearing systems among financial institutions, coordinates clearing matters among financial institutions and provides clearing services. Specific measures shall be formulated by the People's Bank of China.