Receive a call from this number on my iPhone. It's a criminal attempting to commit fraud/theft. The criminal uses a computer recorded message to claim they're the IRS and they're suing for back-taxes.
Firstly, the only official correspondence the IRS sends to citizens, is through the U.S. Post Office.
Secondly, it's against the U.S. Government's own Fair Debt Collection Practices Act to threaten suit without cause, or harass a debtor for debt collection purposes.