Combined Income

• The IRS assists you in calculating combined income with a worksheet provided with Form 1040 instructions. You can estimate combined income by adding your adjusted gross income and nontaxable interest to 50 percent of your annual Social Security benefits. Your total Social Security benefit comes from the SSA-1099 sent at the end of the tax year.
  
  

Taxing Social Security Disability

• If your total combined income exceeds $25,000 and you file your federal taxes as a single person, the IRS taxes your Social Security disability income. This amount is $32,000 if you file taxes as a married individual filing jointly. Your income as a single person with Social Security disability will not likely require payment of federal income taxes on the Social Security amount because your disability limits earned income to about $1,000 a month. Assume you receive $20,000 a year in Social Security disability and $10,000 in earned income. Estimated income before adding your nontaxable interest would be $20,000, because you add only half your Social Security benefit to arrive at combined income. You may pay taxes on Social Security disability if your spouse has income.
  
  

Amount Taxed

• The IRS taxes Social Security benefits depending on your total combined income. If your combined income is between $25,000 and $34,000 as an individual tax filer, it taxes 50 percent of your Social Security disability benefit. The IRS taxes 50 percent of Social Security disability benefits between $32,000 and $44,000 if you file taxes as a married person filing jointly with your spouse. The IRS taxes 85 percent of Social Security benefits for individual filers with a combined income over $34,000 or married filers with a combined income over $44,000. If you are married and file a separate tax return from your spouse although you lived with your spouse at any time during the year, the IRS taxes your Social Security disability benefits at 85 percent.
  
  

Taxation

• The IRS taxes the qualifying percentage of your Social Security benefits as ordinary income. Line 20a of Form 1040 requires your total Social Security disability figure from the SSA-1099. Line 20b adds the percentage of your Social Security disability benefits taxed as calculated from the worksheet. The IRS adds this figure to your wages, taxable interest and dividends, pensions, unemployment compensation and other income to total your gross income. You subtract any adjustments from that figure, including student loan deduction, IRA deduction and moving expenses to arrive at the adjusted gross income figure for the year.