Taxes left unpaid can become a certificate
New Jersey's Division of Local Government Services explains that municipalities use tax sales to enforce unpaid municipal liens and that a certificate can later be redeemed or foreclosed through defined processes. If nobody has paid on the vacant house, ask the title company for the exact payoff. County deed and mortgage records are where the search starts. Do not accept an offer without knowing this figure. That payoff belongs next to the offer when you compare, because it reduces the check you receive.
