It all depends. If the individual or jointly-filing couple
received no additional income,
taxable or tax-exempt, the social security income is not taxed. If, however, the combination of (1) half of social
security income, (2) tax exempt income, and (3) wages, interest, dividends,
alimony, etc. exceed total social
security income without being offset by adjustments, the individual or couple will pay taxes on a portion of the
social security earnings.
The form for calculating what portion, if any, of the social
security income is taxable is on Page 26 of the 2011 Form 1040. I’ve automated
the calculations involved on a spreadsheet. It turns out that if the filer’s
total income from other sources is at or below 75 percent of SS income, net of
any adjustments or deductions, SS is exempted. Thereafter, a portion of the SS
income is taxed, up to a maximum of
85 percent of it.
The instruction booklet is available from About.com (link).