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. Businesses, including sole proprietorships, partnerships, and corporations, may need an EIN to open a bank account, apply for business licenses, or file tax returns. Obtaining an EIN is a straightforward process that can be completed online through the IRS website, and it is essential for compliance with federal tax regulations.