Received a call from this number the other day.  They actually left a message unlike so many other scammers.  They said it was my final notice for the IRS to file suit against us.  First of all it was an automated voice similar to SIRI not even a real person.  Second, they referred the the IRS wrong; the recording referred to themselves as "IRS" not "the IRS".  Third, the IRS would NEVER EVER make calls to you.  They only correspond by mail.  So please do yourself a favor and don't call these jokers back.