For example, you should notify the IRS if your Social Security number was used to file an income tax return; this can be done by submitting a Form 14039 Identity Theft Affidavit. Likewise ...

File Form 14039. Fill out and attach Form 14039, Identity Theft Affidavit, with your paper return. If you receive a letter from the IRS or otherwise suspect you're the victim of ID theft ...

To file an identity-theft affidavit with the IRS, open a support ticket or get a personal pin number, see the agency’s website.