"Earnings" for Social Security Earnings test are wages and self-employment income. The income that you pay FICA taxes on. W-2's are issued for wages. Self-employment is computed on Schedule C and Schedule SE when income taxes are done. Self-employment is for a business; child care, lawn services, handyman are few examples of small businesses. Self-employment also refers to farmers, truckers, plumbers, lawyers, accountants, store owners. Larger businesses tend to be incorporated or partnerships.

Capital gains, interest, most rental income is non-wage, non-earned income and do not affect Social Security benefits even though they may be subject to income taxes. Social Security benefits can be subject to income tax. Wages and self-employment can be subject to income tax.