What is an EIN, and does your business need one?

An EIN. Employer Identification Number, is a nine-digit number the IRS assigns to a business entity, formatted XX-XXXXXXX. Think of it as a Social Security Number for your business: it identifies the business on tax filings, bank paperwork, payroll, and vendor forms.

Despite the name, you don't need employees to need one. The 'Employer' in EIN is historical; today it functions as the general-purpose federal tax ID for businesses, trusts, estates, and nonprofits.

Who actually needs an EIN

Corporations and partnerships are required to have one, no exceptions. LLCs need one in nearly all practical cases: banks require an EIN to open a business account, and multi-member LLCs need it for tax filings. Nonprofits need one before applying for tax-exempt status. Trusts need one once they become irrevocable, and estates need one for probate banking.

Sole proprietors are the one honest exception: with no employees and no retirement plan, you can legally operate using your SSN. Many freelancers still get an EIN to keep their SSN off the W-9 forms they hand to every client, a privacy decision more than a legal one.

How you get one

The IRS issues EINs free of charge. You can apply yourself at irs.gov using the online EIN Assistant (available Monday–Friday, roughly 7 AM to 10 PM Eastern), by fax, or by mail. The online route issues the number in minutes when everything goes smoothly; fax takes one to three weeks; mail takes four or more.

The application itself is IRS Form SS-4, about twenty questions covering the entity type, the 'responsible party' (the person who controls the business, with their SSN or ITIN), the address, and what the business does. Most rejections come from small mismatches: a legal name that doesn't match state records, a responsible-party issue, or a duplicate application.

If you'd rather have it handled, a filing service like ours prepares the SS-4 from plain-language questions, checks it against the common rejection causes, and files it with the IRS as your third-party designee, and the do-it-yourself option is always free.