Children may need to file a tax return if they earned over $2,000. .
Sons or daughters who earn over the $2,000 limit may be considered their own provider or remain a dependent on their parents tax return. If you provided more than half of their income for the year, you can claim them as a dependent and thus claim their deduction. This will reduce your taxes. However, it could also increase their tax liability dramatically.
If the son or daughter paid in income taxes, they may want to file a return in order to get the amounts refunded to them. They can file their own taxes regardless of if they are your dependent or not.