The Social Security program pays benefits to retired and disabled workers and their family members, and to family members of deceased workers. The Social Security program is financed primarily through payroll taxes that are deposited in the U.S. Treasury and credited to the Social Security trust fund. Any revenues credited to the trust fund in excess of program costs (benefit payments and administrative expenses) are invested in special U.S. government obligations (debt instruments of the U.S. government). This book examines the basics of how the Social Security program is funded and how the Social Security trust fund works.