The earlier verification was not complete
The IRS identifies Letter 6167C as an incomplete identity-authentication letter. It can follow correspondence containing incomplete or invalid Taxpayer Protection Program authentication documents.
Use the current instructions
Read what this letter requires rather than repeating an earlier verification attempt without changes. Have the previous IRS letters and the records you already submitted available when seeking clarification.
Handle records securely
Do not upload identification documents to this website or send them to an unsolicited caller. Verify the destination through IRS.gov and the actual correspondence. Keep a record of the steps you complete and any confirmation the IRS provides. If you did not file the return in question, make that clear during the verification process.