I agree legal council is best but read the original decree and the amended one. Just because the changed agreement addressed the custody arrangements it sounds like it did not address the exemption situation ... so from what you are saying is that each parent is to claim one of the kids each tax year. But the 8332 ONLY gives the non custodial parent the right to claim the exemption and the CTC. The HOH filing status, day care credit & EIC still belongs to the custodial parent according to IRS rules which the state courts cannot override.
