Yes — a foster child placed with you by an authorized placement agency or court order can qualify as a "qualifying child" and make you eligible for the Child Tax Credit and other dependent-related benefits, as long as the other requirements are met (age, residence, support). The foster child must have a Social Security number. If the child was placed with you for only part of the year, you may still claim the Child Tax Credit since the child is treated as having lived with you for the entire year in the year of placement in some cases. The Earned Income Tax Credit rules are similar for foster children.