Here's what the real IRS says:
"Don't be fooled by surprise phone calls by criminals impersonating IRS agents with threats or promises of a big refund if you provide them with your private information," said IRS Commissioner John Koskinen. "If you're surprised to get a call from the IRS, it almost certainly isn't the real IRS. We generally initially contact taxpayers by mail."
Scammers make unsolicited calls claiming to be IRS officials. They demand that the victim pay a bogus tax bill. They con the victim into sending cash, usually through a wire transfer or a prepaid debit card or gift card, like an iTunes card. They may also leave “urgent” callback requests through phone “robo-calls,” or via a phishing email.
Many phone scams use threats to intimidate and bully a victim into paying. They may even threaten to arrest, deport or revoke the driver’s license of their victim if they don’t get the money.