It is unjust not to pay the social security contributions required by legitimate authority.
Unemployment almost always wounds its victim's dignity and threatens the equilibrium of his life. Besides the harm done to him personally, it entails many risks for his family.
Catechism of the Catholic Church, 2436
Social Security should provide adequate, continuing, and reliable income in an equitable manner for low- and average-wage workers and their families when these workers retire or become disabled, and for the survivors when a wage-earner dies. USCCB, Faithful Citizenship