An Employer Identification Number (EIN), also known as a Federal Tax Identification Number, is a 9-digit number assigned by the IRS to identify a business. A Tax Id number is also called an Employer Identification Number or EIN. IRS. The IRS issues the EIN. Get Started. DOR. The North Carolina Department of Revenue. EIN, FEIN, TIN, and tax ID, oh my! Your EIN may also be referred to as a Federal Employer Information Number (FEIN) or a Federal Tax.