You know the two certainties of life, death and taxes. Fighting city hall, or the county seat is not an easy or advisable route. The problem was likely with your lender who didn't set up the proper amount to begin with. Regardless who messed up, you likely owe the taxes for the time you owned the property. If the arrangement is too steep, you can ask for an alternate plan, but if you're selling they will need to make it current in order to transfer the title.