Your preliminary adjusted gross income, often referred to as your combined income, measures how much, if any, of your Social Security benefits are taxable. The preliminary adjusted gross income limits can vary from year to year and are different depending on whether you file as single, married filing jointly or married filing separately. Your preliminary adjusted gross income depends on your taxable income, adjustments to income you claim, nontaxable interest and Social Security benefits. For example, if you are single, in 2011 none of your benefits are taxable if your preliminary adjusted gross income falls below $25,000.
Calculate your adjusted gross income by subtracting any adjustments to income you claim from your total taxable income. For example, if you have $19,000 of taxable income and $3,000 in adjustments to income, subtract $3,000 from $19,000 to get $16,000 as your adjusted gross income.
Add any nontaxable interest earned during the year. Continuing the example, if you earned $900 in nontaxable interest, add $16,000 plus $900 to get $16,900.
Multiply your Social Security benefits by one-half. For example, if you receive $6,800 in Social Security benefits, multiply $6,800 by 1/2 to get $3,400.
Add the Step 2 result to half your Social Security benefits to find your preliminary adjusted gross income. In this example, add $16,900 to $3,400 to find your preliminary adjusted gross income equals $20,200.