What organ collects social insurance premiums?

According to the Collection Regulations, the collection agencies of social insurance premiums are determined by the people's governments of provinces, autonomous regions and municipalities directly under the Central Government, which can be determined by tax authorities or social insurance agencies. Social insurance premiums, whether collected by social insurance agencies or tax authorities, can only be collected by one institution within the scope of provinces, autonomous regions and municipalities directly under the central government; Pension, unemployment and medical insurance premiums must be uniformly collected.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.