Is it legal for a company to have another company pay social security on its behalf

Not legal. Social insurance registration implementation of territorial management, account opening and payment unit should be "employer", that is, with the workers to establish a labor relationship with the employer. If the labor contract is signed with the company, the social insurance should be paid in the name of the company, and many companies entrust third parties and use their social insurance accounts to make social insurance contributions, which is not in accordance with the law. Legal basis: According to Article 57 of the Social Insurance Law, "An employer shall, within thirty days from the date of its establishment, apply to the local social insurance agency for social insurance registration on the basis of its business license, registration certificate or seal. The social insurance agency shall examine and approve the application within fifteen days from the date of receipt of the application and issue the social insurance registration document." Article 58 stipulates that "An employer shall apply for social insurance registration for its employees with the social insurance administrative organization within thirty days from the date of employment." China's Provisional Regulations on the Collection and Payment of Social Insurance Premiums clearly stipulate that the collection and payment of social insurance premiums is the responsibility of the social administration department, and that employers must apply for social insurance for their workers in accordance with the law. If the employer has already applied for social insurance for the workers, but the employer does not pay the social insurance premiums for the workers according to the regulations, regardless of the non-payment of social insurance premiums or the refusal to pay the social insurance premiums, the social administration department can force the collection of social insurance premiums according to the law.

Article 57 of the Social Insurance Law Employers shall, within thirty days from the date of establishment, apply to the local social insurance agency for social insurance registration with their business license, registration certificate or seal. The social insurance agency shall examine and approve the application within fifteen days from the date of receipt of the application and issue the social insurance registration document." Article 58 stipulates that "An employer shall, within thirty days from the date of employment, apply for social insurance registration for its employees with the social insurance administration organization. China's Provisional Regulations on the Collection and Payment of Social Insurance Premiums clearly stipulate that the collection and payment of social insurance premiums is the responsibility of the social administration department, and that employers must apply for social insurance for their workers in accordance with the law. If the employer has already applied for social security for the workers, but the employer does not pay the social insurance premiums for the workers according to the regulations, the social management department can enforce the collection of social insurance premiums according to the law, regardless of the non-payment of social insurance premiums or the refusal to pay social insurance premiums.