What does it mean that the social security tax base of Shanghai hukou is the same for 7 years?

It means that the tax base is generally equal to all the wage income of the month, including allowances, bonuses and overtime pay, so the tax is more about bonuses and overtime pay than social security, so in most cases the tax is greater than or equal to social security. The so-called social security is social insurance, which is one of the important components of the social security system. Social security is a social security fund established by national legislation.