This is one of those gory details sorts of questions that generally require an account's input to get right. My advice, for what it's worth, is to prepare your taxes with a "hole" in them, and consider asking the IRS,
themselves, for help.
My completely uneducated guess about how this is going to play out: when they paid that tax for you, they sent you some kind of 1099 form that indicates that they did so. When you figure your taxes, you'll figure them as if that tax had never been paid, but look it has, so therefore you owe that much less. This is exactly the sort of shenannigans that IRS computers probably look for to flag people for auditing, so it's all the more important to get it right with professional help of some sort.