The guy calls me around 8:00 am telling me that I owe money.  His name is Ricky Johnson and is calling from the IRS.  I call the "other number" to get in contact with Michael Carter, 415 251 8504, and I ask him for Michael Carter.  I tell him that I really need to speak with Michael.  The guy tells me that Michael is on holiday, so I grill him asking what holiday it is.  I tell him that the IRS doesn't operate on the weekend and Mike needs to know the difference from holidays and vacations.  He needs a talk from HR.  They'll pick up if you want to troll.  These people are terrible and claim to be a major government institution.   The IRS will usually send a letter or take back taxes/tax related charges out of your following refund.  They'll send a letter before ever calling.