“Hi, I just finalized my divorce this month, in the state of Arizona. My ex and I have 3 children together. In the papers I agreed that my ex would claim the oldest each year, and the youngest every other year. I just went on the IRS website and realized that I did not have to agree to this, the court mediator said I didn’t have a choice that I had to let him claim the children that way because he was paying support for the kids, (althought he hasn’t paid anything since he moved out, a year ago.) I agreed to this, but now I would like to change this; is there any way I can do that? We have joint legal custody, and I have full physical custody. The kids live with me in Oregon year-round, and my ex is supposed to get them six weeks in the summer and every other Christmas for a week.”
While technically whomever has court-ordered physical custody of a child is the one who is entitled to claim that child as a dependent for tax purposes, many states do encourage (some harder than others) parents to share the exemption. Where there is only one child, typically the parents alternate who takes the deduction, with one parent taking it on odd years, and the other parent taking it on even years. Where there are more than one child, typically one parent will always claim one child, and the other parent another child.
The fact that your court mediator said that you “didn’t have a choice” is interesting, and suggests that your divorce was done in a state that is one of the more progressive ones that is concerned more about equity and fairness.
While in theory you could go back to court and insist on taking all deductions, your ex is presumably paying child support, and your demanding all 3 exemptions every year will make you look like a bit of a jerk.