Assuming that there is no labor contract and no labor relationship, the legal representative does not necessarily need to pay social security, but at least one individual in the company must pay.
Units should apply for social security registration certificate at the local social security bureau within one month after registration. This is the account of the company in social security (with a copy of business license, a copy of organization code certificate, a bank account opening permit and official seal).
After completing the social security registration certificate, you will know how to handle social security procedures for employees in the Social Security Bureau. Their staff will give you various forms according to different social security projects. When you come back, you have to ask the management for data.