IRS has revenue agent (auditors who set up adjustments ) and revenue officers (collector of taxes) Also all IRS employees have an employee id which they give you when you talk to them. They will call whatever phone number they have usually getting it off tax returns. We got this phone call from some American woman -- they are equal opportunity employers. IT was federal criminal enforcement action. If we did not return her 2nd attempt to reach us, she wished us "'good luck"
I made a return call to this phone number as it was a robocall with with a case number. I called back and they asked for the case number that I did not have the number, so the operative with a foreign accent asked for my name. I did not give it to him. I asked where he was calling from and he replied Washington, DC, since he told me I had issues with the Feds. Having lived in DC, I asked why his return call stated Springfield, IL? Did not get a satisfactory answer. I advised the operative that he was a grifter.