To determine whether any of your benefits are taxable, compare the base amount for your filing status with the total of one half of your social security payments plus all your income from other sources, including tax exempt interest. If you are married and file a joint return, you must combine your incomes and your social security and equivalent tier 1 railroad retirement benefits when figuring the taxable portion of the benefits.

The taxable amount of the benefits is figured on a worksheet in the Form 1040 (PDF) or Form 1040A (PDF) instruction book, or in Publication 915, Social Security and Equivalent Railroad Retirement Benefits. Refer to Tax Topic 423, Social Security and Equivalent Railroad Retirement Benefits, for base amounts, and additional information regarding taxability and reporting requirements.

References:

• Publication 915, Social Security and Equivalent Railroad Retirement Benefits
• Tax Topic 423, Social Security and Equivalent Railroad Retirement Benefits

Source: www.irs.gov