An EIN, or employer identification number, is a federal tax ID number the IRS issues to businesses, tax-exempt organizations, and other entities, and it's also known as a federal tax identification number.

Despite the name, you don't have to have employees to have one. An EIN is how the IRS identifies a business or entity the way an SSN identifies a person, and it appears in box b of your W-2. You'll also be asked for it when opening a business bank account or applying for business licenses.

This page describes what the IRS says. Whether you need an EIN is a question for the IRS or a tax professional.

What an EIN is

The IRS says an EIN is a federal tax ID number for businesses, tax-exempt organizations, and other entities, and that you can get one for free directly from the IRS in minutes. A business entity should have only one EIN.

It isn't the same as a personal number. An SSN comes from the Social Security Administration and an ITIN from the IRS, and both identify individuals (see ITIN vs SSN). An EIN identifies an entity, though an application needs the SSN or ITIN of the person in charge, called the responsible party.

The IRS says you need an EIN if you have employees, will pay employment, excise, or alcohol, tobacco, and firearms taxes, or withhold taxes on income other than wages paid to a nonresident alien. You also need one to operate a partnership, LLC, corporation, tax-exempt organization, estate, trust (with certain exceptions), or retirement plan. If you don't need one for federal tax purposes, you can still request one for banking or state tax purposes.

What's on it

The number itself is just nine digits, so the useful paper is the confirmation the IRS gives you. These are the pieces worth knowing.

Item What it is What to check
EIN confirmation notice (CP575) The IRS notice verifying the number it assigned Business name and entity type are spelled correctly
Letter 147C An IRS letter confirming an EIN previously assigned, which you can request Use it if you can't find your original notice
Entity name The name you gave when applying, matching your formation documents Matches state registration
Responsible party The person in charge of the entity and its assets Still accurate; nominees aren't authorized to apply
Entity type Sole proprietor, partnership, LLC, corporation, trust, and so on Matches how you file taxes
Application date When you applied Useful if you used "Applied For" on a return

The IRS offers three ways to confirm your EIN: request an entity transcript, download a digital CP575 from a Business Tax Account, or request Letter 147C.

What to keep and for how long

Keep your EIN confirmation notice for as long as the business or entity exists. The IRS says it can't cancel an EIN, only deactivate it, so the number outlives your activity. A new EIN is generally needed when your entity's ownership or structure changes, for example when a sole proprietor incorporates or forms a partnership. You don't need a new one just because you change your name, address, or responsible party.

For tax records, the IRS says to keep records supporting income, deductions, or credits until the period of limitations runs out, and to keep employment tax records for at least 4 years after the tax becomes due or is paid, whichever is later.

If you can't find the number, the IRS suggests looking at the notice, past business returns, your business bank, and state or local license paperwork. See what documents to keep and how long for the wider picture.

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