If you are positive that you didn't already e-file your return on an earlier date (or did the non-filer stimulus registration) and you are sure that you are not eligible to be claimed as a dependent by someone else, you may be a victim of identity theft. You will have to file a paper return instead of e-filing. When you print your return for paper filing, also complete IRS Form 14039, Identity Theft Affidavit (PDF). Use a fillable form at IRS.gov, print it, then attach the form to your return and mail your return according to instructions.
You can access IRS resources on identity theft here.
TurboTax also has resources on identity theft here.
where do you see this since you say you haven't filed? did you submit and it was rejected?
Sounds like trouble, as in tax fraud! As they say, there are three certainties in life: Death, taxes, and identity theft!
This happened to us several years ago. Unfortunately you'll have to just jump through the hoops with a variety of reports to fill out. After all is said and done, the IRS will provide you with a Personal Identity Number (PIN) that you'll have to use to file your taxes from now on. Good luck! It really sucks that criminals can make our lives more miserable while stealing from us taxpayers!