Got this call about 8:30 in the morning. It was a call claiming to be the IRS, threatening me with a lawsuit and asking me to return the call. I knew it was a scam right away, because:
A. According to the official IRS website, the real IRS will NEVER call to threaten you with a lawsuit.
B. The caller ID showed that the number came from a CELL PHONE. No legitimate IRS employee that I know of would call someone about back taxes from a cell phone.
C. My workplace pays all of my taxes, except for a few local ones which I cover almost immediately anyway, so the IRS have no real reason to contact me about back taxes.
D. For that matter, although I've never actually gotten legit calls about back taxes (obviously since I've never even received physical correspondance), I'm almost certain the real IRS would only direct people to call an official IRS line (like their 1-800-829-1040 line), and never a random line, much less a cell phone line as stated above. And even so, I live in Pennsylvania so I have no idea why this scammer wants me to call a Kansas line.
If you get a call from this number, block it and then report it to the IRS and the FTC immediately - DO NOT return the call or you'll encourage the scammer to continue calling you.