The Internal Revenue Service uses Employer Identification Numbers, or EINs, to identify businesses for tax purposes. Most businesses, including some sole proprietorships, need one. When you apply for and receive an EIN, the IRS will automatically generate a confirmation letter, or notice, and mail it to you. If you lose the letter, or never received it, you can call the IRS to have them issue you a new one.
Who to Contact
If you've lost or misplaced your EIN, the IRS advises that you call its Business & Specialty Tax Line at (800) 829-4933, Monday through Friday between 7:00 a.m. and 7:00 p.m. local time. Once you provide proof of your identity over the phone, an IRS service representative will look up your number for you, and, if you wish, mail a physical copy of the confirmation letter to you. If you only need the number itself, and not the confirmation letter, you may be able to find it on one of your tax returns from a previous year.