Legal basis: People's Republic of China (PRC) Social Insurance Law.
Article 12 The employing unit shall pay the basic old-age insurance premium according to the proportion of the total wages of employees stipulated by the state and record it in the basic old-age insurance pooling fund.
Article 58 An employing unit shall, within 30 days from the date of employment, apply to the social insurance agency for social insurance registration for its employees. If the social insurance has not been registered, the social insurance agency shall verify the social insurance premium it should pay. Employees-free individual industrial and commercial households who voluntarily participate in social insurance, part-time employees who do not participate in social insurance in the employing unit and other flexible employees shall apply to the social insurance agency for social insurance registration. The state establishes a national unified personal social security number. Personal social security number is a citizen's identity number.