There is another one around, an automated message supposedly from HMRC saying a 'charge has been placed on this address'. Paul has had it at his business and I've had it at home. We contacted our Accountants and they confirmed that HMRC would only contact you by paper (letter), never by phone or e-mail. The call invites you to press 1 to be connected to your 'case officer' or you can phone them back on the number they give you.