The taxable part of your Social Security income depends on your total income and your filing status. When your Modified Adjusted Gross Income (MAGI) exceeds the base amount for your filing status, some of your Social Security income is taxable. TurboTax calculates the taxable part of your Social Security income when you enter all of your income.
Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0
To see the Social Security Benefits Calculation Worksheet in Turbo Tax Online version you would have to save your return with all the worksheets to your computer. Or if you are using the Desktop CD/Download Software you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the right side.