Income to the trust funds

• Employment taxes—taxes paid by employees, their employers, and self-employed persons
• Income from the taxation of benefits
• Interest on investments (see information on interest rates)
• Other income (reimbursements from the general fund of the Treasury for various costs imposed on the program, gifts from individual citizens, etc.)

Cost (i.e.outgo or expenditures) from the funds

• Benefit payments—may include payments for vocational rehabilitation services to disabled beneficiaries and reductions for unnegotiated checks
• Annual transfers to the Railroad Retirement program for its role in collecting Social Security taxes and paying Social Security-equivalent benefits
• Administrative expenses

Surpluses, deficits, and asset reserves
The difference between total income and total cost for a particular period of time is the net increase in the trust fund for that period. If this amount is positive, we say the fund had a surplus; if negative, the fund ran a deficit. The sum of all surpluses and deficits since the beginning of the program equals the asset reserves of the trust funds.

Almost all trust fund asset reserves are invested in securites backed by the full faith and credit of the Federal government. Data on such investments are updated monthly