Any individual claiming standard deductions and credits and does not need to itemize deductions, does not own a business and earns less than $100,000 can fill out a 1040A income tax form, as of 2015. The 1040A is slightly more complicated than the 1040EZ, but more simple than the 1040.
When a taxpayer's finances become more complicated, such as with added dependents or filing jointly, he must use Form 1040A or 1040. The 1040A is shorter and simpler, but only allows the standard deduction, limited types of income, limited income adjustments and limited options for credits to claim. Those who need to include more specific information or who are claiming types of income not eligible need to use the 1040 form.