IRS scam. Don't answer, or block the number, or play with them. I like to call them back using a line where caller ID is blocked (anonymous) and play with them until they get frustrated. If you keep it up long enough and keep calling them they will take the line out of service. Do not call them if your caller ID is active otherwise they can harass you further and obviously don't give them any personal info. Just tell them what you think of their mothers and that sort of thing until they give up and take the line out of service.
I got the call from this number. It startled me. I called back to pretend to pay back the taxes and left a message.
The number that called me back was from Jamaica - (876)571-4695.