Total scam. This is the 5th call I've received claiming that I'm be sued by the IRS. 4 were from Texas and 1 from Washington state.
I did not return any of them. Calls will likely increase since it's close to tax filing time.
Called at 5:30 A.M. and left message that the IRS was filling a lawsuit against me. A friend had this same call so I looked up the number and found this thread. Glad to have confirmation it's a hoax!