To most of us, the word "dependent" is synonymous with "child," but the IRS's definition is a little different. For tax purposes, a dependent must be either a "qualifying child" or a "qualifying relative."
To be a qualifying child, the child must:
Live in your home for over half the year
Be your child, stepchild, adopted child, or foster child or your brother, sister, or step sibling (or a descendant of any of these)
Be under 19 or a student under 24 and be younger than you (or be permanently and totally disabled)
Not provide over half of his or her own support for the year
Be a U.s. citizen or a resident of either the U.s., Canada, or Mexico (with an exception for certain legally adopted children)
Not file a joint return for the year
However, even if a child does not meet all of these requirements, he or she may still satisfy the qualifying relative test.
A qualifying relative:
Meets the last two requirements in the above list (a joint return is allowed if the sole purpose for filing is to obtain a refund)
Receives more than 50% of his or her support from you
Has gross income of no more than $3,950 (for 2014)
Is related to you or is a member of your household (as these terms are defined in the tax law)
To obtain the dependency exemption, you will have to include the dependent's Social Security number on your tax return. Special rules may apply if you and your child's other parent are divorced or separated.
These rules can sometimes be complex to apply. Let us know if you have questions.