If you and he each own half, you and he are each responsible for half the taxes. It seems fair to pay all taxes out of escrow so that you each paid half. Unless the divorce stated you were to pay all the taxes, you do not owe him anything.
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Unless your divorce decree states otherwise, I don't believe you are legally obligated to pay him. Paying him would probably be the fair thing to do, but I don't think that is what you are asking.
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