These are scam artist(s) posing as IRS agents claiming in a voice message that they are investigating tax evasion by the party they called [you]. Don't call back the number they tell you to call. If they call and you pick up the phone, don't provide any info they ask for including anything about your identity, location, phone numbers, etc.

Just got a call from someone named "Don Ross" saying I was under investigation for tax evasion. He is supposedly from the "Criminal Investigation Unit" of the IRS, but he said they were filing a civil lawsuit. It doesn't work that way. They can get any money the feel they are entitled to through a criminal action. Anyway, it's all [***]. But it did just about scare the hell out of me for a few minutes. [***]. I hope the guy dies.

Got a prerecorded call from this number with an accented voice telling me that I was under investigation for fraud by the IRS and to call a certain number to discuss this at a certain time in my local area code. Call was on a Saturday which seemed odd.

Message was cut off but also indicated that I was being investigated for tax evasion.  Need to know where these types of scams can be reported to for further investigation.

Got a voicemail last night guy by the name Agent Ross saying I was under investigation and to call between 9am to 4pm. I always search number and check, I know my taxes are fine.