Just got the same call last night (at 5:50pm) - robot-sounding voice - saying that the IRS is suing me and that there is a "non-bailable arrest warrant" out for me. Did not bother to call back, because the IRS will not try to arrest you without visiting in-person first.
Total scam.
i just received this call claiming to be the irs threatening a lawsuit I answered the phone no one was there called the number back and rings busy everytime