What Is an EIN?

An EIN (Employer Identification Number) is a nine-digit tax ID number the IRS assigns to businesses — like a Social Security number for your business. You need one if you have employees, operate as a corporation or partnership, or open a business bank account. Sole proprietors without employees can often use their Social Security number instead, but many prefer an EIN for privacy. You can get an EIN instantly for free at IRS.gov. You'll need your EIN when filing business tax returns, applying for business licenses, and more.