J.K. Lasser's Your Income Tax 2013: For Preparing Your 2012 Tax Return

34.3 Computing Taxable Social Security Benefits

The taxable portion of your 2012 benefits depends on your provisional income and your filing status. Part of your net Social Security benefits (Box 5 of Form SSA-1099) will be subject to tax if your provisional income exceeds a base amount of $25,000 or $32,000. The base amount is $25,000 if your filing status is single, head of household, qualifying widow(er), or married filing separately and you lived apart from your spouse for all of 2012. The base amount is $32,000 if you are married filing jointly. You are not entitled to any base amount if you are married filing separately and you lived with your spouse at any time during 2012; see the Caution in this section.

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Caution

Married Filing Separately

If you are married filing separately and during 2012 you lived with your spouse at any time, you must include in your taxable income the lesser of (1) 85% of your net Social Security benefits shown on Line 1 of Worksheet 34-1 or (2) 85% of the provisional income shown on Line 8 of Worksheet 34-1.

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To figure provisional income, you will have to increase the total income shown on your return by tax-exempt interest (4.24), by 50% of your net Social Security benefits, and by certain tax-free fringe benefits and exclusions, before subtracting adjustments to income other than the student loan interest ...