My dad died in 2016. I paid his state taxes due in 2017. Can I deduct them?

[Carl]

I'm sorry for your loss. But no, you can not deduct the taxes you paid on behalf of someone else, even if they passed away. That's because you are not "legally" obligated to pay them. Any taxes or other debts owed by your father after he passed should have been paid from his estate. If the estate did not have the assets necessary in order to pay the taxes or debts, then that's not your problem or issue. If the person to whom the debt is owed, or the entity to whom the taxes are owed want to sue, penalize or fine a deceased person, they are welcome to do so. They are not going to get that which does not exist.