Q: Can the IRS overrule a court document for claiming dependants.

A: In general, the person who provides more than half the support for the dependent is entitled to claim the exemption for that dependent on their tax return. However, exemptions for dependents can be allocated between former spouses by agreement. It is quite common in divorce cases for spouses to allocate the tax attributes in this manner. It sounds like there is a provision in your marital separation agreement ("MSA") saying you are entitled to the exemption. If I had to guess, your son's mother has continued claiming him as a dependent despite the provision in the MSA. The IRS computer is set up to catch when two returns are filed listing the same person as a dependent. If your ex-wife filed her return first, claiming your son, then your return would have tripped the system and resulted in adjustments. But the proper response to the adjustments would be to provide a copy of the MSA and proof that you have been, at all times, current with your support payments, and the IRS should have adjusted your ex-wife's return and left yours alone. You may be able to file amended tax returns to reverse the IRS adjustments, but you may want to hire counsel in order to do this as the amended returns will almost certainly be subjected to scrutiny with regard to the exemption. In addition, there is a limited time for you to do this. You have only until 4/15/16 to file an amended return for your 2012 taxes in order to claim any refund due to you. For the years before 2012, I'm afraid you're out of luck unless you have made any payments within the last two years.