Who Must File

• Requirements for filing tax returns depends on your age, income, and filing status. Married couples under 65, for example, need not file if their combined income does not exceed $17,900 (for 2008). Single taxpayers face a lower cutoff, and elderly and disabled taxpayers enjoy a higher cutoff (see the IRS 1040 Instructions in References below for details).
  
  

Forms

• Under most circumstances individuals are required to file either Form 1040 or Form 1040EZ. Form 1040EZ is simpler and is your best option if your finances are simple and you don't intend to itemize your deductions. Form 1040 is better if you intend to itemize your deductions instead of taking the standard deduction.
  
  

Filing Status

• Your filing status will determine the amount of your standard deduction and it varies with your marital status. Married taxpayers filing jointly with their spouses receive favorable treatment in several respects, including the amount of the standard deduction (which lowers taxable income) and the income threshold below which it is not necessary to file a tax return. Accordingly, if you are married you should file jointly with your spouse. Heads of households also receive favorable treatment for the standard deduction.
  
  

Claiming Dependents

• You will be given the opportunity to lower your taxable income by claiming as a dependent anyone you support, including yourself. The more dependents you have, the lower will be your taxable income. Just make sure that nobody you're claiming as a dependent is claiming himself as well, because this inconsistency will likely be noticed by the IRS.
  
  

Automatic Extensions

• You are entitled to an automatic extension of six months without penalty as long as you file IRS Form 4868 by April 15. Remember that Form 4868 must only be postmarked by April 15---it need not be received by the IRS by that date.
  
  

Late Penalties

• There are two types of late penalties: failure to file on time and failure to pay on time. These penalties are graduated and top out at 25 percent of your unpaid tax bill or $100, whichever is greater. You only have to pay the lesser of these penalties even if both apply. Since these penalties are based on the amount you owe, if you owe the IRS nothing, there is no direct penalty for failure to file a return even if your income exceeds the filing cutoff. But remember that if you're relying on certain exclusions (such as the Foreign Earned Income Exclusion) to reduce your tax bill to zero, you may lose the exclusion if you fail to file, because the IRS may consider the exclusion waived due to failure to claim it on time.