Left recorded message claiming that it was the Internal Revenue Service, and I (or my attorney of record) needed to return the call "the second you receive this message" as it is "extremely time sensitive". Yeah. Sure. NOTHING the IRS does is "extremely time sensitive", and their first contact with you will ALWAYS be by US Postal Service. Sure sounds like a scam to me.
left a recorded message that it was the IRS, not to ignore the call, and return the call before they take action. End of message was "thank you and take care." Seriously, big scam call