WASHINGTON (AP) — The Internal Revenue Service has been doing business with nearly 1,200 vendors that owe back taxes, including one unnamed contractor that owed a whopping $525 million, a new inspector general's report says. Altogether, 1,168 IRS vendors owed back taxes totaling $589 million as of July 2012, according to the report released Tuesday. Only 50 were in a payment plan to pay off their debt.