Not sure what state you are in, so you should consult with an experienced divorce attorney in your state. But generally the decree, as an order of the court, should be followed and judges don't like it when people ignore their orders. In general, as long as the medical expenses were reasonable and necessary, he shouldn't be able to get off the hook on some technicality that you didn't tell him about it. However, I agree with the first answer that the actual language of the court's order is important as to what it required from both parents. Sounds like your ex is just bluffing to keep you from demanding money from him and that you would benefit from getting an attorney yourself and going after your ex for not paying his share.

