These calls are not coming from the IRS or anywhere else in the US government.
Here is a story from FOX 13, Tampa Bay, Florida about these calls. It's the best explanation I've found so far of these calls as well as what to do when you receive one and to whom to report the call and how:
I also received a call from this number and he left a garbled message stating he was Jim Arthur from a crime investigative division and there was an error on my tax return and I should call back immediately. He even gave an agent number of 1593. I will call back when pigs fly!
My call was from Jason Blake also heavily accented saying he was from criminal investigations and I have done some kind of tax fraud and I am hiding it from the federal government. I had 2 messages from this guy and I called the police
I'm in the Boston area, and just Googled and found this thread. The guy first asked for the person who originally had this number, and I said it was the wrong number. He claimed he couldn't hear me and after saying the third time it's the wrong number he then asked for me by name. I asked who it was and he said "client investigation services". I said to take my name off the list and please don't call again. Before I said goodbye, he threatened that I would be arrested. I definitely had to laugh it off. That's when I Googled this number. He did not give a name.
Logan Smith, badge # 0143 called. Thanks everybody for listing these things. Since my story is exactly in line with everyone elses, there is obviously nothing to worry about. Either that, or we'll meet once we all get arrrested!