The Social Security program pays benefits to retired or disabled workers and their family members, and to family members of deceased workers. Program income and outgo are accounted for in two separate trust funds authorized under Title II of the Social Security Act: the Federal Old-Age and Survivors Insurance (OASI) trust fund and the Federal Disability Insurance (DI) trust fund. This report refers to the two trust funds as an aggregate Social Security trust fund and discusses the operations of the OASI and DI trust funds on a combined basis. This report covers the basics of how the Social Security program is financed and how the Social Security trust fund works. It will be updated annually to reflect current projections of the financial status of the Social Security trust fund.