Since you have shared custody was tax information included in your custody orders? This is usually something that's mentioned and if you have shared custody then it normally says one can claim every other year and the other gets the other years. Look through your papers and see, you might be surprised to find it.

If this is not mentioned then whoever had the child the most during the year is the one who gets to claim the child. Living with her mother or not, if she made any income at all (child support is income) and she had the child the most days during the year, then she gets to claim the child on her taxes.

If you had the child more days during the year then you can claim the child (again, as long as there is no court order for something specific to be followed). Never having been married to the mother doesn't change the fact that it's your child.

Also, if she doesn't plan to claim the child, or is otherwise trying to let her mother claim the child or something like that, then you get to claim the child as the next parent. If she lets her mother claim the child, and you claim him too, the IRS will give the credits and deductions to you as the parent.

Because years do not have an even number of days, keeping a calendar of who has the child when could benefit you if you have shared physical custody and equal time. One person is guaranteed to have the child at least one more day than the other person. You could also go back to court and request an order for this to simplify matters though.

The rules for never-married parents aren't quite as clean-cut as we might like them to be. As long as the two parents, combined, provide more support than any other source, then the parents can choose between themselves who claims the child's dependency exemption.

But only the person with whom the child lived for more than half the year, can claim either Head of Household filing status or the Earned Income Tax Credit. Most of the benefit of claiming a child comes from the EITC.

If grandma owns the house and the child's mother isn't paying rent, then grandma is providing a big chunk of the child's support (the value of the housing). It is also possible, if the mother doesn't work or has a small income, that grandma has a good claim on both the dependency exemption and the EITC.