Federal tax lien issue on abandoned home

[William Miller]

The scenario, found an owner of a bando property. Sub says lost it to bank. After checking title commitment to close bank appears to have vacated the foreclosure. There are back taxes owed $4K in property taxes, and a $19K Federal tax lien. Seller says he didnt know of any back owed taxes. My question. How to best deal with the Fed lien? Just pay it off? Negotiate a payoff? Trust?