Understanding Your Letter 5071C or 6331C, Internal Revenue Service Identity Verification for IRS Letter Recipients
To process a federal income tax return, you need to verify your identity.
To verify your identity, go to our secure Identity Verification Service.It is available 24 hours a day.
You can call the toll-free IRS Identity Verification telephone number if you prefer.
The taxpayer must call us together and participate on the call if they want authorized third parties to assist them.
The IRS Identity Verification number is only for identity verification.There is no other tax related information available.
We can't process your tax return, issue refunds, or credit overpayments until we hear from you.