Income Thresholds: Single Taxpayers

• Single taxpayers under the age of 65 must file an income tax return if they have incomes of at least $9,350 as of tax year 2011. Those over age 65 must file if their income was more than $10,750. Qualifying widows or widowers with dependent children must file if they have incomes of $15,050 -- or $16,150 if they are older than 65. This threshold is reviewed periodically. For tax years after 2011, you can find the filing thresholds for the year in the instructions for filling out IRS Form 1040, 1040A or 1040EZ.
  
  

Income Thresholds: Married Taxpayers

• If both members of a married couple are older than 65, they must file if their combined income is at least $20,900. If one member is under 65, they must file if their combined incomes are less than $19,800. If both are under 65, they must file if combined incomes are greater than $18,700. Taxpayers who are married and plan to file separately must file if their income was at least $3,650.
  
  

Self-Employment Income

• Where people who work for someone else have Social Security payments deducted from their income and then matched by their employer, self-employed workers must pay both parts of that contribution. If you had income from self-employment of at least $400, you must file a Form 1040-SE. This is the form the IRS uses to assess and track your Social Security and Medicare tax, also called self-employment tax.
  
  

What Doesn't Count as Income

• Certain forms of income are not deemed taxable. Loan proceeds from life insurance policies, dividends from life insurance policies and income you take out of Roth individual retirement accounts that are designated as Roth accounts in 401k and 401b plans are not taxable. If this is your only source of income, you do not necessarily have to file a tax return. You may wish to anyway, though, if you qualify for a tax credit. If your employer withheld income taxes from your pay, you may be entitled to a refund. But you must file a return to collect it.
  
  

Special Situations

• You must file if you owe alternative minimum tax, if you owe additional tax on a retirement plan or other qualified plan such as a 401k or if you owe household employment taxes. You must also file if you owe taxes on tips you did not report to your employer or if you received more than $108.28 from a tax-exempt organization that does not withhold Social Security taxes.