Your dependent files their own tax return. However, if your dependent's total income received from all sources for the entire tax year is less than $12,300, they are not required to file a tax return at all.
If any taxes were withheld from the W-2 income and the total income received was less than $12,300 for the year, the dependent "might" want to file to get those withheld taxes refunded to them. They can file their own tax return for absolutely free at http://www.freefile.com/
