Automated call that left me a voicemail saying it was the IRS and that they were filing a lawsuit against me. I was supposed to call the number back. Definitely thinking it's a scam; I'm off to do more internet searching.

I got the same automated call / voicemail. They also said they were filing a lawsuit against me and left an area code 360, prefix 362 phone number to call. (360-362-4719) The call back number has been reported to be associated with a number of different scams. They do NOT claim to be the US federal IRS they claim to be Internal Revenue Services (plural). Clearly a scam that I'll be reporting to the Feds.

I also got a message from 720 592 6544 on 3-17-15 saying that they were the IRS and had been trying to reach me and were filing a lawsuit against me.  I did not have a pen so did not get the call back number.  I know the IRS would send a letter first.