The minimum income requirement for filing a tax return is the standard deduction for that year plus the deduction for one dependent. Because the exact amount for these deductions changes each year, so does the minimum income requirement.
The minimum income requirement also varies based on filing status and age. For example, the 2013 minimum income requirement for a single person under age 65 was $10,000, but for a married couple over age 65 filing jointly, the minimum was $22,400. People who fall under the minimum can still file a tax return to receive a refund, but they are not required to do so.