Yes. A legally placed foster child is the same as a biological child, for tax purposes. Note that the support requirement is not whether you provided support, but only that the child didn't support himself. This means you (usually) don't need to worry about calculating his support for the time you did not have him.
A child (including adopted, foster & step) of a taxpayer can still be a “Qualifying Child” (QC) dependent, regardless of his/her income, if:
- 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
- He did not provide more than 1/2 his own support. Scholarships are considered third party support and not as support provided by the student.
- He lived with the parent (including temporary absences such as away at school) for more than half the year
A couple of caveats: 1. the parents may may file a competing claim for the child resulting in IRS letters. That usually means you will have to prove the child lived with you for more than half the year. 2. the parent may claim that time with you was only a temporary absence from their home.
