A child of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
1. He is under age 19, or under 24 if a full time student for at least 5 months of the year, or is totally & permanently disabled
2. He did not provide more than 1/2 his own support
3. He lived with the parent (or was away at school) for more than half the year
So, it doesn't matter how much he earned. What matters is how much he spent on support. Money he put into savings does not count as support he spent on him self.
A person can still be an other dependent (Qualifying relative in IRS parlance, even though they do not have to actually be related), if not a Qualifying Child, if he meets the 6 tests for claiming a dependent:
1. Closely Related OR live with you ALL year
2. His/her gross taxable income for the year must be less than $3,900 (2013)
3. You must have provided more than 1/2 his support
In either case:
4. He must be a US citizen or resident of the US, Canada or Mexico
5. He must not file a joint return with his spouse or be claiming a dependent of his own
6. He must not be the qualifying child of another taxpayer
