Fake IRS call threatening legal action and jail if one doesn't respond and pay a fine, just the usual sand-negers hoping to scam and extort another witless victim.
This is indeed a SCAM - they don't say who they are with but that there are five lawsuits being filed at the end of the day and an federal agents will be coming to arrest you unless you call immediately. And the only "advise" they have if this call is ignored is "Good Luck to you". I called my local police and they said it is a scam. The IRS only communicates via US Postal Service. Gave me a good chuckle.