The IRS may be aware of identity theft before you are. In that case, they will send you an identity theft letter.
Identity Theft Letter Types
Identity theft is not a joke.
Scammers sometimes use stolen Social Security numbers to file fraudulent tax returns and collect refunds. To prevent this, the IRS scans every tax return for signs of fraud. If the system finds a suspicious tax return, the IRS reviews the return and sends a letter to the taxpayer letting them know about the potential ID theft. The IRS won’t process the suspicious tax return until the taxpayer responds to the letter.
You may receive one of these letters if your tax return seems like it may have been filed by an identity thief:
Letter 5071C, Potential Identity Theft with Online Option: This letter will tell you to use an online tool to verify your identity and tax return information. If you didn’t file, then you can let the IRS know with the online tool.
Letter 4883C, Potential Identity Theft: This letter tells you to call the IRS to verify your identity and tax return information. If you didn’t file, then you can call the Taxpayer Protection Program hotline number on the letter.
Letter 5747C, Potential Identity Theft In Person Appointment: This letter tells you to verify your identity and tax return information in person at a local Taxpayer Assistance Center. If you didn’t file, then you can call the Taxpayer Protection Program hotline number on the letter.
Letter 5447C, Potential Identity Theft Outside the U.S.: This letter tells you to use an online tool or to call the IRS to verify your identity and tax return information. If you didn’t file, then you can let the IRS know with the online tool.
To Sum Up
The identity theft letter will tell you the steps you need to take. You should follow those steps to resolve the matter with the IRS. You will either have to verify your identity over the phone, in person or online depending on what letter you receive.
You can find more resources on reporting and recovering from ID theft with the Federal Trade Commission: identitytheft.gov.
Identity Theft Affidavit
If you have already received an IRS identity theft letter, then you don’t need to file an identity theft affidavit. However, If you need to give the IRS a heads up that you're a victim of identity theft or that you think you may be a victim, you can file Form 14039, Identity Theft Affidavit.