The IRS has certain income thresholds (based on filing status) that require an income tax return to be filed. It depends on what the students income was as to if the student is required to file taxes for the academic aid year they are applying for.
Beginning with the 2017–18 FAFSA, students will be required to report income and tax information from an earlier tax year. Because the FAFSA will ask for older income and tax information, you will already have done your taxes by the time you fill out your FAFSA, and you won’t need to estimate your tax information and then go back into the FAFSA later to update it.
Because you’ll already have done your taxes by the time you fill out your FAFSA, you may be able to use the IRS Data Retrieval Tool (IRS DRT) to automatically import your tax information into your FAFSA. (Learn about the IRS DRT at https://fafsa.ed.gov/fotw1718/help/irshlp9.htm)