Who is the purpose of ss tax?

To fund the Social Security program.

The SS program pays old age and disability pensions to covered workers.

The SS tax has been taking in much more than is needed to cover the costs of the program. The excess has been used for general federal government programs. The federal government has issued itself preferred bonds promising to repay itself the excess when the SS tax begins to take in less than the cost of the SS program. The collection of these bonds is called the "Social Security Trust Fund."