It depends.
According to the instructions for Form 14039, Identity Theft Affidavit, you can submit by either mail or FAX.
Per the instructions, to submit by mail,
- If you checked Box 1 in Section B in response to a notice or letter received from the IRS, return this form and if possible, a copy of the notice or letter to the address contained in the notice or letter.
- If you checked Box 1 in Section B of Form 14039, are unable to file your tax return electronically because the primary and/ or secondary SSN was misused, attach this Form 14039 to the back of your paper tax return and submit to the IRS location where you normally file your tax return.
- If you’ve already filed your paper return, please submit this Form 14039 to the IRS location where you normally file. Refer to the ‘Where Do You File’ section of your return instructions or visit IRS.gov and input the search term ‘Where to File’.
- If you checked Box 2 in Section B of Form 14039 (no current tax-related issue), mail this form to: Department of the Treasury Internal Revenue Service Fresno, CA 93888-0025
