@claytonvon1
There is a support worksheet in publication 501 that may help to answer this question.
To try and be brief. The child‘s support needs include room and board, tuition, clothing, medical care, travel and entertainment. Support that the child pays for himself includes money that the child spends on any of those things that comes from the child’s own sources, including income, savings, or student loans taken out in the child’s own name. If the child does not spend money on himself, but either spends it on other people (such as a girlfriend or their own child) or saves it, then it does not count as support the child provides himself. Support provided by the mother, in this case, would include a percentage of the mother’s housing expenses, including rent or mortgage payment, utilities, insurance, and household groceries. For example, if there are three people living in the household, then 1/3 of the mother’s housing expenses count as support that she provides to the child. You may also provide direct support, such as in the form of paying tuition, or covering the child on your health insurance, or paying child support to the mother or directly to the child.
If the child is a full-time student under the age of 24, then it does not matter who provides the support, as long as the child does not provide more than half his own support. If he does not provide more than half his own support, and if he lives in the mother’s home more than half the nights of the year, then the mother can claim him as a dependent without reference to your child custody order, because the order is not enforceable as far as the IRS is concerned once the child is emancipated under state law.
If he meets these tests, then his income is irrelevant, as long as he does not spend it on his own support to the level of “more than half”.
If he was not a full-time student, then he falls under a different category of dependent and there is a strict income limit of $4300 in that case. Note that “full-time student“ means that the child was a full-time student as defined by the school, for at least one day in at least five different months of the year. That means that a high school student who graduates in May or June will generally be considered a full-time student for the entire year even if they don’t go to college.
