The IRS has many security measures in place to verify the accuracy of tax returns and the validity of social security numbers (SSNs) or individual taxpayer identification numbers (ITINs) submitted.

If you receive a notice from the IRS that leads you to believe someone may have used your SSN (or ITIN) fraudulently, please notify the IRS immediately by responding to the name and number printed on the notice or letter.
If you’re an actual or potential victim of identity theft and would like the IRS to mark your account to identify any questionable activity, please complete Form 14039, Identity Theft Affidavit. See the “Instructions for Submitting this Form” in Form 14039, for information on submitting it by mail or fax.
You may also contact the IRS for specialized assistance at 800-908-4490. These IRS employees are available to answer questions about identity theft and resolve any tax account issues that resulted from identity theft.
Review Publication 5027, Identity Theft Information for Taxpayers, for more information. It’s available in English and Spanish.