So what you're saying is 'yes'? I'm the policyholder so I would be on the hook no matter who signed the AOB at time of service? Am i still responsible for 60% of this bill? I can only as the NCP to pay his share of unreimbursed expenses?
Yes. you would be the one that is billed. However, make sure you have reviewed your custody agreement: it may have a clause for splitting unpaid medical expenses. If not, you will get the bill. If this is a big problem (with your ex taking your son to the ER rather than an urgent care or the childs pediatrician) it could be worth it to take it to court for modification (as in requesting you split unpaid medical expenses) I would ask, not sure if the judge would order it, but ask for the father to be solely responsible for unpaid ER visits. This is becoming a big deal with insurance companies balking at paying high ER bills for a cough, or sniffle, or ingrown toenail.