The real IRS described years ago how delinquent tax is not collected:
IRS Warns of Pervasive Telephone Scam - 31 Oct 2013
http://www.irs.gov/uac/Newsroom/IRS-Warns-of-Pervasive-Telephone-Scam
"The Internal Revenue Service today warned consumers about a sophisticated phone scam targeting taxpayers, including recent immigrants, throughout the country.
Victims are told they owe money to the IRS and it must be paid promptly through a pre-loaded debit card or wire transfer. If the victim refuses to cooperate, they are then threatened with arrest, deportation or suspension of a business or driver’s license. In many cases, the caller becomes hostile and insulting.
... we do not and will not ask for credit card numbers over the phone, nor request a pre-paid debit card or wire transfer ... the first IRS contact with taxpayers on a tax issue is likely to occur via mail."
Of course, this advice will soon become less valid if the HANGUP Act or something similar never gets passed to counteract the foolish TCPA exemption slid into the current Budget Act.