IRS Letter 6217C.

"We've completed a review of your account and determined the employer identification number (EIN) application information we have on file is no longer valid".

Again, no change in anything.  I've now got 12 clients with this.  I see posts on "Tax ProTalk" with other accountants getting the same letter.  It is a valid letter, but it would be better for them to ask for confirmation before assigning a new EIN.  That is where the problem lies.