Message left saying there were irregularities in my taxes [UN-true] and IRS was threatening "criminal" charges.  Caller had my first name right, but not last.  Last name was Asian and caller had such a thick Asian accent that I had to play it several times to get everything.  Probably looking for immigrants who don't understand our laws and have a knee-jerk fear of authority.

The IRS does NOT call with threats of any kind.  They start with a questioning letter so people will call them.  It's a lot cheaper for them to staff a phone bank that receives calls than to pay people to try to catch taxpayers at a given number.