File an IRS Form 14039 (Identity Theft Affidavit) as soon as possible to let the IRS know that someone is using your identity. You can also call the IRS at 1-800-908-4490.
If you received a 5071C Letter from the IRS, it means the IRS received a return with your name and/or Social Security number and suspects it may not be from you. The IRS sends this letter to verify your identity and confirm whether or not you submitted the return.
If someone filed a return in your name, visit IdentityTheft.gov for tips to recover from identity theft.