What Is a TIN Number for Business and How to Get One?

A Taxpayer Identification Number, or TIN, is the nine-digit number the IRS uses to track your business’s tax filings and payments. For most businesses, the TIN you need is an Employer Identification Number (EIN), which the IRS issues for free directly through its website, by fax, or by mail. Which TIN number for business use applies to you depends on your legal structure, whether you have employees, and whether you’re eligible for a Social Security Number.

Which TIN Your Business Needs

The IRS assigns different types of nine-digit TINs for different situations.¹ Three of them matter to business owners:

An Employer Identification Number (EIN) is the standard business tax ID for corporations, partnerships, and LLCs. It functions like a Social Security Number for the business itself.
A Social Security Number (SSN) works as the tax ID for a sole proprietor with no employees. A single-member LLC that hasn’t elected corporate treatment also generally uses the owner’s SSN for federal income tax reporting.²
An Individual Taxpayer Identification Number (ITIN) is for people who must file a U.S. federal return but aren’t eligible for an SSN, such as a non-resident alien or a foreign business owner.

Federal law requires the correct identifying number on any return, statement, or other document you file.³

When You Are Required to Get an EIN

You need an EIN if any of the following apply to your business:⁴

You have employees, even one.
You operate as a corporation, partnership, or multi-member LLC.
You file employment, excise, or alcohol, tobacco, and firearms tax returns.
You withhold taxes on income (other than wages) paid to a non-resident alien.
You run a retirement plan, trust, estate, or tax-exempt organization.

Why Sole Proprietors Often Get One Anyway

A sole proprietor with no employees can legally use an SSN, but doing so puts that number on every W-9 you hand to a client and every 1099 they issue. An EIN keeps your SSN off those forms and lowers your exposure to identity theft. It’s free and takes minutes online, so many sole proprietors get one even though they aren’t required to.

What to Gather Before You Apply

The EIN application is Form SS-4. The online session times out after 15 minutes of inactivity, so have your information ready before you start.⁵ You’ll be asked for:

The legal name of the entity, exactly as it appears on your formation documents.
Any trade name or DBA the business operates under.
The name and SSN, ITIN, or EIN of the responsible party. The IRS defines this as the individual who ultimately owns or controls the entity and its assets.⁶
Your entity type: sole proprietorship, partnership, corporation, LLC, nonprofit, trust, or other.
Your reason for applying, such as starting a new business, hiring employees, opening a bank account, or creating a retirement plan.
The number of agricultural, household, and other employees you expect to hire in the next 12 months.

How to Apply for an EIN

Applying is free through the IRS. You should never pay a fee, and the IRS specifically warns against third-party sites that charge for the service.⁷

Online

The online application is the fastest route and issues your EIN immediately on approval. The tool is available Monday through Friday from 6:00 a.m. to 1:00 a.m. Eastern, Saturdays from 6:00 a.m. to 9:00 p.m., and Sundays from 6:00 p.m. to midnight. You can submit only one application per responsible party per day, and you must have a legal residence or principal place of business in the United States or a U.S. territory.⁸

Fax

Faxing a completed Form SS-4 generally gets you an EIN within four business days. Include a return fax number so the IRS can send the confirmation back.⁸

Mail

Mailing Form SS-4 takes about four to five weeks. Plan ahead if you have a hard deadline for opening an account or filing a return.⁸

Phone (International Applicants Only)

If your business has no legal residence or principal office in the United States or its territories, call 267-941-1099 (not toll-free), Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern. The caller must be authorized to receive the EIN and answer questions about the form, and if the IRS representative requests it, you must mail or fax the signed Form SS-4 within 24 hours.⁸

After You Get the Number

The IRS confirms your new EIN with Notice CP 575. Store it somewhere safe. You’ll want it to open a business bank account, apply for credit, and verify your tax ID with the IRS later.

Getting an ITIN as a Foreign Business Owner

If you must file a U.S. federal tax return but aren’t eligible for an SSN, apply for an ITIN using Form W-7. The form generally has to be attached to the front of the federal return you’re filing and mailed to the IRS ITIN Operation in Austin, Texas. Certain exceptions let you apply without a return attached.⁹

You must document both your identity and your foreign status. A valid passport is the only single document that proves both. Without one, you need two documents (one for identity, one for foreign status), and at least one must include a photo. The IRS accepts items like a national identification card, foreign voter’s registration card, visa, civil birth certificate, or foreign driver’s license.¹⁰ Documents must be originals or certified copies from the issuing agency; notarized copies are not accepted. Applying in person at a designated IRS Taxpayer Assistance Center lets staff verify your originals and hand them back on the spot.

If You’ve Lost Your EIN

Check your original CP 575 notice first, then previously filed tax returns and any bank or licensing agency where you used the number. If you still can’t find it, call the IRS Business and Specialty Tax Line at (800) 829-4933, Monday through Friday from 7:00 a.m. to 7:00 p.m. local time. The caller must be an authorized representative of the business.¹¹

When a Business Change Requires a New EIN

Some structural changes mean your existing EIN no longer works and you have to apply for a new one:¹²

A sole proprietor incorporates.
A corporation merges into a new corporation; the surviving new entity needs its own EIN.
A corporation converts to a partnership or sole proprietorship, or vice versa.

Changing only your business name or address doesn’t require a new EIN. You notify the IRS of those changes separately.

Penalties for a Missing or Wrong TIN

Failing to include a correct taxpayer identification number on a required document carries a penalty of $50 per failure, capped at $100,000 per calendar year.¹³ Unlike many other IRS penalties, the $50 amount is not adjusted for inflation and stays the same across tax years.¹⁴ The IRS can waive it for reasonable cause, but the reliable way to avoid it is to get the right number in place before you start filing.

1
Cornell Law School. Taxpayer Identification Number (TIN)
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Internal Revenue Service. Single Member Limited Liability Companies
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Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers
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Internal Revenue Service. Employer Identification Number
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Internal Revenue Service. Form SS-4 – Application for 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. Get an Employer Identification Number
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Internal Revenue Service. Instructions for Form SS-4 (12/2025) – Section: How To Apply for an EIN
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Internal Revenue Service. Instructions for Form W-7 (Rev. December 2024)
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Internal Revenue Service. ITIN Supporting Documents
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Taxpayer Advocate Service. Getting an EIN
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Internal Revenue Service. When to Get a New EIN
13
Office of the Law Revision Counsel. 26 USC 6723 – Failure To Comply With Other Information Reporting Requirements
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Internal Revenue Service. 20.1.7 Information Return Penalties