An Employer Identification Number (EIN) is a unique nine-digit number assigned by the Internal Revenue Service (IRS) to businesses for tax identification purposes. It is often referred to as a Federal Tax Identification Number and is used to identify a business entity in various tax-related documents. EINs are essential for businesses that have employees, operate as a corporation or partnership, or need to file certain tax returns. Obtaining an EIN is a straightforward process that can be completed online through the IRS website, and it helps streamline tax reporting and compliance for businesses.