There have been numerous reports of persons impersonating IRS agents/agencies as scams to obtain personal information for purposes of identity theft crimes. The IRS has published some warnings for specific cases in which both email and snail mail approaches have been found.

While I haven't heard of any "personal appearances" in which fraudulent contacts have been made, it is exceedingly rare for an IRS agent to "show up at your place of business," as they simply don't have enough agents to do that. They DO NOT send notices by email, but may mail you a demand for information, or a demand that you come to their office.

You DO HAVE THE RIGHT to demand identification from anyone claiming to represent a US Government agency.

In the case of anything received in the mail, you can, and in case of questionable demands should, independently contact a known IRS office and request verification that what you see is from an authorised agent and is for IRS official purposes.

John