After retirement, I found that the unit underpaid social security cases.

You can bring a lawsuit to the people's court and demand compensation from the user. The Supreme People's Court's Interpretation on Several Issues Concerning the Application of Laws in the Trial of Labor Dispute Cases (3) Article 1: The people's court shall accept a dispute in which the employer fails to go through the social insurance formalities and the social insurance agency can no longer handle it, resulting in the workers being unable to enjoy the social insurance benefits.

Legal objectivity:

Article 16 of the Social Insurance Law of People's Republic of China (PRC) * * * Individuals who participate in the basic old-age insurance will receive the basic old-age pension on a monthly basis if they have paid for fifteen years at the statutory retirement age. Individuals who participate in the basic old-age insurance and pay less than fifteen years when they reach the statutory retirement age can pay for fifteen years and receive the basic pension on a monthly basis; Can also be transferred to the new rural social endowment insurance or urban residents' social endowment insurance, enjoy the corresponding pension insurance benefits in accordance with the provisions of the State Council. Article 86 of "People's Republic of China (PRC) Social Insurance Law" * * * If the employer fails to pay the social insurance premium in full and on time, the social insurance premium collection agency shall order it to pay it within a time limit or make up for it, and from the date of default, an overdue fine of 0.5% shall be charged on a daily basis; Failing to pay within the time limit, the relevant administrative departments shall impose a fine of more than one time and less than three times the amount owed.