If she is living with you, dont worry about him. He is just being money hungry and chanses are he wont win since you are her sole provider.

He may not lose your son as a deduction. If your son is going to college as a full time student your husband would still be able to deduct him off of his taxes. If your son is not going to school full time then the deduction is going away. Since you both agreed initially on which child you would take you he can take you to court to try to revise the agreement but will most likely lose. I can't say don't worry about it because you never know with the courts. However, the child is living with you and you are providing support in addition to your ex. It's his fault for not thinking ahead when the decree was agreed to. If your son is not going to college then, you might want to go ahead and agree that as long as he stays out of school you are ok with a decrease in child support. Most states child support ends when the child turns 18. It sounds like your decree covered you in case your children went to school. Since college is expensive it would be fair for your ex to help pay for some of the expenses of college with child support. The advantage you have if you agree in advance to the reduction in child support for your son with the stipulation of as long as he does not attend college is that it takes away the real need to go to court. My husband and his ex come to agreement on things all the time rather than go through the expense of attorneys and the courts. If your husband only has the matter of income tax left when he is denied you can ask the courts to award you attorney fees since his taking you to court was frivolous. You may get them because the court really doesn't like it's time to be wasted.

Things like negotiating who can claim the kids for tax dependents is in the property settlement of your divorce decree, it's not on your child support order. He can have child support modified, but he can't have your divorce decree modified. That's done.

Child support is a separate court order from your divorce decree, and he can't renegotiate your divorce property settlement 8 years down the road any more than you can ask him to now repay you for a credit card bill you took on when you divorced.