What Is an EIN (Employer Identification Number)?

Do You Need an EIN?

The fastest way to answer this is to separate "required" from "recommended." The IRS requires an EIN in a specific set of situations, and outside of those, plenty of small businesses get one anyway because it makes ordinary business life easier. Knowing which side of that line you're on saves you from both unnecessary paperwork and a scramble later.

You Are Required to Get an EIN If You

• Have employees, or are about to hire your first one.
• Operate as a corporation (including an S-corporation) or a partnership — including a multi-member LLC, which the IRS taxes as a partnership by default.
• File employment, excise, or alcohol/tobacco/firearms tax returns.
• Withhold taxes on income, other than wages, paid to a nonresident alien.
• Have a qualified retirement plan (such as a Keogh or solo 401(k)).
• Are involved with certain trusts, estates, nonprofits, farmers' cooperatives, or plan administrators.

You Probably Don't Need One — But Likely Want One

If You are a sole proprietor or a single-member LLC with no employees and no excise-tax obligations. In that case the IRS lets you use your own Social Security number to file. Most owners in this position still get an EIN, and for good reasons: banks generally require one to open a business checking account, clients and vendors ask for it on Form W-9, and using an EIN instead of your SSN on all that paperwork keeps your personal number out of circulation and lowers your identity-theft exposure. It also makes your business look established, and it's free — the practical answer for most growing one-person businesses is "yes."

A Note on State and Local IDs

An EIN is your federal number. Depending on where and how you operate, you may also need a separate state tax ID for state income-tax withholding, unemployment insurance, or sales tax — those are issued by your state, not the IRS, and the EIN doesn't replace them. If payroll and multi-state registration are on your horizon, this is one of the areas an HR or PEO partner routinely handles so nothing gets missed.

EIN vs. SSN, ITIN, and TIN

These acronyms get tangled constantly, and the confusion is understandable — they're all nine-digit numbers tied to taxes. The simplest way to keep them straight: TIN is the umbrella term for every tax ID, and the SSN, ITIN, and EIN are specific types of TIN underneath it. The key difference is who or what each one identifies — a person or a business — and which agency issues it.

The Practical Takeaways

• An EIN identifies a business; an SSN and ITIN identify people. When a form asks for your "business tax ID" or "FEIN," it wants your EIN.
• A sole proprietor can use either. With no EIN, you file business taxes under your SSN; once you get an EIN, you can keep the SSN off vendor and bank paperwork.
• Don't substitute one for the other. The IRS specifically asks you not to use an EIN in place of an SSN or ITIN, or vice versa — each has its lane.
• You may also run into PTINs and ATINs. A PTIN identifies a paid tax preparer and an ATIN is a temporary number for a child in the process of adoption — neither has anything to do with running your business.

Step-by-Step Guide to Applying for an EIN

1. Form Your Legal Entity First (If Applicable): If you're creating an LLC, corporation, or partnership, register it with your state before you apply, so the EIN attaches to the correct legal name. Sole proprietors have no entity to form and can apply whenever they're ready. Tax-exempt organizations should wait until they're legally formed.
2. Identify Your Responsible Party: The IRS requires you to name a responsible party — an actual person who owns or controls the business — and provide their SSN or ITIN. It can't be another company (except for government entities) or a nominee like a hired agent. For a single-owner business that's usually you.
3. Gather Your Information: Have ready your legal business name exactly as registered, any trade name (DBA), a physical street address and a mailing address, your entity type, the reason you're applying, your principal business activity, the date the business started, and your expected number of employees. The IRS only accepts letters, numbers, hyphens, and ampersands in business names.
4. Choose Your Application Method: Online is the fastest and is available to businesses whose principal location is in the U.S. or its territories. Fax and mail use the paper Form SS-4. Phone applications are reserved for international applicants without a U.S. presence. Use only one method per entity so you don't accidentally end up with two numbers.
5. Apply Online Through the IRS EIN Assistant: Go straight to IRS.gov and use the free EIN Assistant. You must finish in a single session — it times out after about 15 minutes of inactivity and can't be saved partway — and it's available during posted hours (roughly Monday through Friday, 6 a.m. to 1 a.m. Eastern, with limited weekend hours). When you complete it, your EIN is issued immediately.
6. Or Apply by Fax or Mail: Complete Form SS-4 and fax it (if you include a return fax number, you'll typically get the EIN back in about four business days) or mail it (allow about four weeks). Either way, keep a copy of what you submitted.
7. Save Your Confirmation Notice: The IRS issues a CP 575 confirmation letter — online applicants can download and print it on the spot. Store it where you can find it; it's the official record of your number, and the IRS generally won't issue a duplicate.
8. Put It to Work and Keep It Current: Use the EIN to open your bank account, set up payroll and tax deposits, and complete W-9s. If your responsible party or address ever changes, report it to the IRS within 60 days using Form 8822-B. Remember the IRS limit of one EIN per responsible party per day.

How to Find or Recover a Lost EIN

Misplacing your EIN is common and rarely a crisis — your number is almost certainly already recorded in several places. An EIN is permanent and never reused, so you're recovering an existing number, not getting a new one. Work through the easy sources first, and call the IRS only if you come up empty.

Where to Look First

• Your CP 575 confirmation notice: The original letter the IRS sent when your EIN was assigned.
• Prior business tax returns: Your EIN appears at the top of any return you've filed.
• Bank and loan paperwork: The bank where you opened your business account, or any lender, has it on file.
• Licenses and prior filings: State or local business license applications, and old payroll forms or 1099s you've issued, all carry the number.

If You Still Can't Find It

Call the IRS Business & Specialty Tax Line at 800-829-4933, open Monday through Friday, 7 a.m. to 7 p.m. local time (Alaska and Hawaii follow Pacific time). After verifying that you're authorized to receive it — an owner, partner, corporate officer, or similar — the IRS will give you the number over the phone. If you've somehow ended up with more than one EIN and aren't sure which to use, the same line can tell you which is correct.

When You Need a New EIN

An EIN is meant to be permanent, so you keep the same one through most of a business's life. As a rule of thumb, a structure change usually means a new EIN, while a name, address, or ownership-stake change usually doesn't. The IRS publishes specific scenarios by entity type — here are the ones small businesses hit most often.

When a New EIN Is Generally Required (by Entity Type)

• Sole proprietor: Incorporate, take in partners and become a partnership, are subject to a bankruptcy proceeding, or buy or inherit an existing business you'll run as a sole proprietorship.
• Partnership: Incorporate, have one partner take over and operate it as a sole proprietorship, or end the old partnership and begin a new one.
• Corporation: Receive a new charter from the secretary of state, become a subsidiary of another corporation, change to a partnership or sole proprietorship, or form a new corporation after a statutory merger.

You Generally Do NOT Need a New EIN When You

• Change your business name.
• Change your location or add other locations.
• Operate multiple businesses under the same sole proprietorship.
• Elect S-corporation treatment for an existing corporation, or have an LLC that already has an EIN elect corporate tax treatment.
• Reorganize in a way that changes only the corporation's identity or place, or convert at the state level without changing the underlying structure.

Conversions can get genuinely technical — particularly LLC elections and corporate mergers, where keeping an existing EIN may be possible or even preferable to protect licenses and tax attributes. When a real structure change is on the table, confirm the requirement against the IRS's "When to get a new EIN" guidance, and loop in a CPA or your HR/PEO partner before you file, because the EIN question usually rides along with final returns, payroll transitions, and benefits.

EIN Compliance Checklist

An EIN doesn't carry ongoing filings of its own, but a few habits keep it from becoming a problem at exactly the wrong moment. Use this as a quick backbone — for getting the number, storing it, and keeping its information accurate as your business changes. None of it is complicated, and an HR or PEO partner can carry the recordkeeping and the payroll-side pieces if you'd rather not track them yourself.

Getting & Storing It

1. Entity registered with the state first, if you're an LLC, corporation, or partnership.
2. EIN obtained free directly from the IRS — no third-party fee paid.
3. A correct, qualified responsible party named, with their SSN or ITIN.
4. CP 575 confirmation notice saved somewhere you can find it, with a backup copy.
5. Only one EIN obtained per entity, using a single application method.

Keeping It Current

1. Responsible-party or address changes reported to the IRS within 60 days on Form 8822-B.
2. Business name as used with the IRS kept consistent with your registration.
3. The EIN — not your SSN — used on W-9s, bank accounts, and vendor paperwork.
4. Any state tax IDs (withholding, unemployment, sales tax) obtained separately as needed.

When Things Change

1. A structure change (incorporating, forming a partnership, certain mergers) checked against the IRS's "new EIN" rules before filing.
2. An unneeded EIN handled correctly — the IRS can't cancel an EIN, but it can close the business account on request.
3. A CPA or HR/PEO partner consulted for conversions, mergers, or anything tangled up with payroll or final tax returns.

Topics

What You Use an EIN For

• Hiring & Payroll: Required to report and deposit employment taxes, file payroll returns, and run payroll once you have employees.
• Banking & Credit: Used to open a business bank account, apply for business loans or credit cards, and build a business credit profile separate from your personal credit.
• Licenses & Permits: Frequently required on applications for state and local business licenses and permits.
• Vendor & Client Paperwork: The number you put on Form W-9 so clients can issue you a 1099, and that you use to issue 1099s to your own contractors.
• Tax Filing: The identifier on your business tax returns and on filings for trusts, estates, and retirement plans.

Who Does What

• Owner / Responsible Party: Applies for the EIN, is named as the IRS contact for the entity, and is responsible for keeping that information current. In a small business this is usually one person.
• CPA / Accountant: Advises on whether and when you need an EIN or a new one, especially around entity formation, S-corporation elections, conversions, and mergers.
• HR / PEO Partner: Handles the work that depends on the EIN — payroll setup and employment-tax deposits, new-hire reporting, and state account registrations — and keeps the recordkeeping clean, which is the specialist load a small company can't justify hiring for full-time.
• IRS: Issues the EIN free of charge, maintains the business tax account, and is the place to recover a lost number or report changes.

Key Compliance Considerations

• One Per Responsible Party Per Day: The IRS limits EIN issuance to one per responsible party per day, across all application methods.
• Free From the IRS: There's never a government fee. Paid "EIN filing" services are optional middlemen, not the IRS.
• Keep Information Current: Report responsible-party and address changes within 60 days using Form 8822-B.
• Beneficial Ownership Reporting: Separate from the EIN, some corporations and LLCs may have to report their beneficial owners to FinCEN — confirm whether your entity is covered, as these rules have shifted.
• State IDs Are Separate: An EIN is federal; state withholding, unemployment, and sales-tax IDs are issued by your state and aren't replaced by the EIN.

Frequently Asked Questions