Qualifying child
A child who passes the IRS tests for relationship, age, residency and support, so you can claim tax benefits for them.
To be your qualifying child, the child generally must be your son, daughter, stepchild, foster child, sibling or a descendant of one of them, live with you for more than half the year, and not provide more than half of their own support.
The age test depends on the benefit. For the child tax credit, the child must be under 17 at the end of the year. For the EITC, under 19, or under 24 if a full-time student, or any age if permanently and totally disabled.
Example
A 9-year-old who lives with you all year is a qualifying child for both the child tax credit and the EITC. A 17-year-old can still count for the EITC but not the child tax credit.