Anyone who has income above the threshold set by federal law must file an income tax return with the Internal Revenue Service. According to IRS.gov, the threshold varies based on a variety of factors. Additionally, requirements for state returns vary according to the state's tax laws.
The IRS website provides a filing requirement chart that most taxpayers can use to determine their income threshold for filing a federal income tax return. The threshold varies based on filing status, age and type of income. For example, for the 2014 tax year, individuals under 65 whose filing status is single must file a return if their income is at least $10,150. Alternatively, individuals who are married filing jointly and are both over 65 years old must file a return if their income is at least $22,700. These thresholds may change year to year. The IRS provides a calculator on its website that collects tax information and determines whether a return must be filed for the previous year.
Some states require individuals to also file a state tax return if they must file a federal return, according to Intuit, which operates the online Turbotax filing service. Other states only require filing if income exceeds a certain level. On their website, the company provides a list of links to each state's filing requirements, if applicable.