What Is a Federal Employer Identification Number?

A Federal Employer Identification Number, usually called an EIN, is a nine-digit number the IRS assigns to a business, nonprofit, trust, estate, or similar entity to identify it for tax purposes. It functions as a Social Security number for the entity. The IRS issues it free of charge, the number is permanent once assigned, and most businesses other than solo sole proprietors are required to have one.

The number comes in a two-plus-seven format (XX-XXXXXXX). Once the IRS assigns it to your entity, it stays with that entity forever. Even if you close the business, the IRS will not cancel the number or reassign it to anyone else.

Who Needs an EIN

If your business has employees, you need an EIN to report and pay employment taxes. That applies whether you operate as a corporation, partnership, LLC, or sole proprietorship.

Employees are not the only trigger. You also need an EIN if your entity is any of the following, even with no payroll:

A corporation
A partnership
A limited liability company (LLC)
A tax-exempt organization
An estate or trust (except certain revocable trusts owned entirely by the grantor)

You also need one if you withhold taxes on income paid to a nonresident alien, or if you file excise or alcohol, tobacco, and firearms tax returns.¹

The Sole Proprietor Exception

Sole proprietors are the main group that can skip the EIN. If you have no employees, no Keogh retirement plan, and no excise tax obligations, you can use your personal Social Security number for all federal tax purposes. Many sole proprietors still choose to get an EIN so they don’t have to hand out their Social Security number to clients and vendors, but the IRS does not require one in that situation.¹

How to Apply

You apply by completing IRS Form SS-4. The IRS charges nothing for an EIN regardless of which method you use.²

Online

This is the fastest route. If your principal place of business is in the United States or a U.S. territory, and you have the responsible party’s Social Security number or Individual Taxpayer Identification Number, you can apply through the IRS website and receive your EIN immediately on approval.²

Fax

Complete Form SS-4 and fax it to the IRS under the Fax-TIN program. You’ll generally receive your EIN by return fax within four business days.³

Mail

You can mail Form SS-4, but plan ahead. The IRS recommends submitting by mail at least four to five weeks before you’ll actually need the number.³

Phone (International Applicants Only)

If your principal place of business is outside the United States, the online tool is not available to you. Call 267-941-1099 (not toll-free) between 6:00 a.m. and 11:00 p.m. Eastern time, Monday through Friday. Have a completed Form SS-4 ready before you call. The representative will walk through the information and assign your EIN over the phone, and if asked, you must mail or fax the signed form within 24 hours.⁴

One Per Day, and Don’t Pay a Fee

The IRS limits issuance to one EIN per responsible party per day across all methods, so if you’re setting up several entities, you’ll need to space them out.²

The IRS is blunt on cost: “You never have to pay a fee for an EIN.” Various third-party sites charge anywhere from $50 to $300 to submit the application for you, but they’re filing the same free IRS form. Unless an accountant or attorney is handling it as part of broader business formation work, there’s no reason to pay.²

What You Use an EIN For

Once assigned, the EIN becomes the number you use in nearly every official interaction your business has with government agencies and financial institutions:

Opening a business bank account. Banks require an EIN (or a Social Security number for sole proprietors) to open a business account, and keeping business funds separate from personal funds also helps with liability protection.⁵
Payroll filings, W-2s, and employment tax returns.
Federal and state tax returns, so the IRS can match filings to the right account.
State and local business licenses and permits, which commonly ask for the EIN.⁶
Applications for business credit, since lenders use the EIN to pull business credit reports.
Information returns such as Form 1099-NEC. All 1099 filers must have an EIN, and it must appear on every information return filed.⁷

When a Change Forces a New EIN

An EIN is tied to a specific entity structure. Change the structure in a fundamental way and the old number no longer fits. A name change or an address change alone never triggers a new EIN. The IRS lists the triggers by entity type:⁸

Sole proprietors need a new EIN if they incorporate, form a partnership, or declare bankruptcy.
Corporations need a new EIN if they receive a new charter from the secretary of state, convert to a partnership or sole proprietorship, or merge to create a new corporation. Subsidiaries get their own EIN.
Partnerships need a new EIN if they incorporate, if one partner takes over as a sole proprietor, or if the partnership dissolves and a new one starts. An ownership change that doesn’t terminate the partnership does not require a new EIN.
LLCs need a new EIN if an existing LLC terminates and a new corporation or partnership forms, or if a single-member LLC begins filing excise or employment tax returns.
Trusts need a new EIN when a revocable trust becomes irrevocable, a living trust converts to a testamentary trust, or a living trust terminates by distributing property to a residual trust.

The pattern is consistent. Structural changes that create a legally different entity require a new EIN. Administrative changes like renaming, moving, or updating a trustee’s address do not.⁸

Finding an EIN You’ve Lost

Losing track of an EIN is common, especially for older businesses. Check these first:

The original IRS confirmation notice, CP 575, sent when the EIN was assigned.
Any previous federal tax return your business has filed.
Prior IRS correspondence, which includes the EIN on notices and letters.
The bank where you opened the business account.

If none of those work, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7:00 a.m. to 7:00 p.m. local time. You’ll need to verify your identity before the representative can share account information.⁹

For publicly traded companies, EINs appear on SEC filings and can be found by searching annual and quarterly reports through the SEC’s EDGAR database.¹⁰

Closing an EIN You No Longer Need

The IRS cannot cancel an EIN or reassign it, but it can deactivate the account so no future filings are expected. First, file all outstanding returns and pay any balance owed. Then send a letter to the IRS with your entity’s EIN, legal name, address, the EIN assignment notice if you still have it, and the reason for deactivation. Mail it to one of these addresses:¹¹

Internal Revenue Service, MS 6055, Kansas City, MO 64108
Internal Revenue Service, MS 6273, Ogden, UT 84201

Tax-exempt organizations use the Ogden address (Attn: EO Entity, Mail Stop 6273) and can also fax the letter to 855-214-7520.¹¹

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Internal Revenue Service. Employer Identification Number
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Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025)
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Internal Revenue Service. Instructions for Form SS-4
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U.S. Small Business Administration. Open a Business Bank Account
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U.S. Small Business Administration. Get Federal and State Tax ID Numbers
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Internal Revenue Service. Publication 1099 General Instructions for Certain Information Returns
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Internal Revenue Service. When to Get a New EIN
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Internal Revenue Service. Telephone Assistance Contacts for Business Customers
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U.S. Securities and Exchange Commission. EDGAR Full Text Search
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Internal Revenue Service. If You No Longer Need Your EIN