Is it legal for human resources companies to pay social security?

Legal. It is necessary for both parties to sign a remittance agreement. Social insurance is the most important part of the social security system. When discussing the history of social insurance, we can't separate social insurance from social security. Social insurance refers to the system that the state establishes a social insurance fund through legislation to give necessary material help to workers who participate in labor relations when they lose their ability to work and are unemployed. Social insurance is not for profit.