Based upon your email, I believe you have a dispute with the children’s father over the dependent child tax exemptions for which you should prevail so long as you can demonstrate he did not pay the full amount of child support and had an arrearage at the end of 2015. However, the solution is not so comfortable. The solution will likely be for you to claim the children and recognize that the IRS might contact you concerning duplicate claim of the dependent child tax exemption for the children. He would be the one to lose the benefit if you can prove to the IRS to their satisfaction that he was not current on his support at the end of 2015. He should sign form 8832 for you but if he refuses, you can pursue him in the domestic court here for a signature. That may take several weeks so if you are anxious to file your taxes, you will have to go the route that leaves both of you potentially at risk of audit. I’m not aware of any way you can invalidate his claim of the dependent child tax exemption before just filing your taxes and claiming the children. I would suggest assessment with a tax lawyer for a more concrete response as to negotiating this issue with the IRS. We have tax attorneys here at Robinson & Henry and one of them may be able to provide you with more guidance on this issue.