Another fake IRS call where the scam artists phone you up pretending to be the IRS and that the IRS has filed a lawsuit against you. They expect you to call them back and then use non-standard untraceable ways of stealing from you, such as prepaid credit cards or Green Dot.

Here's an article from the real IRS about this kind of scam.
https://www.irs.gov/uac/irs-warns-taxpayers-o ... unes-gift-cards

If these scammers call you, you should report them to federal law enforcement at this link.
https://www.treasury.gov/tigta/contact_report_scam.shtml