A business tax ID is a nine-digit number the IRS assigns to identify your business for tax purposes

A tax ID number for a business, officially called an Employer Identification Number or EIN, is how the Internal Revenue Service tracks your business's tax filings, payroll, and other financial records. It works the same way your Social Security number works for personal taxes — it's the identifier the IRS uses to match your business to its tax returns and accounts.

You need an EIN if you have employees, operate as a partnership or corporation, or file certain types of business tax returns. Even if you're self-employed as a sole proprietor with no employees, you may still want one to keep your personal and business finances separate. The EIN is free to obtain and takes only a few minutes to request.

Key Takeaways

  • An EIN is a nine-digit number assigned by the IRS to identify your business for tax purposes, separate from your personal Social Security number.
  • You must have an EIN if you have employees, operate as a partnership or corporation, or file business tax returns as anything other than a sole proprietor.
  • You can request an EIN for free online through the IRS website, by mail, by fax, or by phone, and you'll receive it when ready online or within a few weeks by mail.
  • An EIN is required to open a business bank account, hire employees, and file payroll taxes with the IRS.
  • Once assigned, your EIN does not change even if your business structure or ownership changes, unless you dissolve the business entirely.

When you must have an EIN

The IRS requires an EIN in specific situations. If you have any employees — even one part-time worker — you must have an EIN to file payroll taxes and report wages. If your business is structured as a partnership, corporation, S-corporation, or LLC with multiple owners, you need an EIN. If you operate as a sole proprietor with no employees, you can use your Social Security number on your tax return, but many sole proprietors get an EIN anyway to keep business and personal finances separate.

You also need an EIN if you file certain business tax returns, such as Form 1065 (partnership return), Form 1120 (corporate return), or Form 1120-S (S-corporation return). If you're a nonprofit organization, you must have an EIN. If you're a trust or estate, you typically need one as well. The IRS website has a full list of situations requiring an EIN, organized by business type.

How to request an EIN online

The fastest way to get an EIN is to request one online through the IRS website at irs.gov. Go to the "explore for an EIN" page and follow the interactive form. You'll need your Social Security number or ITIN, your business name and address, the type of business structure you have, and the reason you're requesting an EIN. The form takes about 10 minutes to complete.

When you submit the form online, the IRS issues your EIN when ready on the screen. You can print the confirmation page right away and use that EIN to open a bank account or file returns. The IRS will also mail you a formal notice (Form SS-4) within two weeks. Keep both the printed confirmation and the mailed notice in your records.

Other ways to request an EIN

If you prefer not to explore online, you can mail Form SS-4 to the IRS address listed on the form itself — the address depends on which state your business is in. Processing by mail takes about four weeks. You can also fax Form SS-4 to the IRS fax number for your state, which also takes about four weeks.

If you need an EIN urgently and cannot use the online system, you can call the IRS Business and Specialty Tax Line at 1-800-829-4933. You'll speak to a representative who can assign an EIN over the phone and mail you the formal notice. Phone lines are typically available Monday through Friday, 7 a.m. to 10 p.m. Eastern time. Have your business information ready before you call.

What information you'll need to provide

When you request an EIN, have the following information ready: your legal business name (exactly as it appears on your business registration or formation documents), your business address, your mailing address if different, the type of business structure (sole proprietor, partnership, corporation, LLC, nonprofit, etc.), your Social Security number or ITIN, and the reason you're requesting an EIN (opening a new business, hiring employees, changing business structure, etc.).

You'll also need to know the principal business activity — what your business actually does. The IRS uses a classification system called NAICS codes (North American Industry Classification System) to categorize businesses. If you're unsure of your code, the IRS website has a searchable list. For example, a plumbing business might be classified under "Plumbing, Heating, and Air-Conditioning Contractors," and a consulting firm under "Management, Scientific, and Technical Consulting Services."

How to use your EIN once you have it

Your EIN is required on several important documents. You'll use it on your business tax returns, on payroll tax forms if you have employees, on your business bank account process, and on any contracts or agreements where you identify your business to vendors or clients. You'll also provide it to your accountant or tax preparer so they can file your returns correctly.

When you hire employees, you'll use your EIN to register with your state's labor department and to set up payroll withholding. If you explore for a business loan or business credit card, the lender will ask for your EIN. Some vendors and suppliers may also ask for it when you open a business account with them.

What happens if your business structure changes

If you change your business structure — for example, converting from a sole proprietorship to an LLC or from an LLC to a corporation — you generally keep the same EIN. The IRS does not reassign numbers when ownership or structure changes. However, if you dissolve your business entirely and later start a completely new business, you'll need to request a new EIN for the new business.

If you're unsure whether a change to your business requires a new EIN, contact the IRS or consult a tax professional. Some structural changes, like adding a partner to a sole proprietorship, do require a new EIN because the business structure itself has changed. The IRS can clarify your specific situation.

Frequently Asked Questions

Can I use my Social Security number instead of an EIN?

If you're a sole proprietor with no employees, you can use your Social Security number on your tax return instead of an EIN. However, many sole proprietors request an EIN anyway to keep personal and business finances separate and to protect their Social Security number from being widely shared with vendors and clients.

How long does it take to get an EIN?

Online requests are processed when ready — you receive your EIN on the screen and can use it right away. Mail and fax requests take about four weeks. Phone requests are processed during the call, and you'll receive a formal notice in the mail within two weeks.

Is there a fee to get an EIN?

No. The IRS does not charge any fee to request or obtain an EIN. Be cautious of third-party websites that offer to obtain an EIN for you — they charge fees for a service you can do yourself for free on the IRS website.

What if I lose my EIN or forget it?

You can look up your EIN by calling the IRS at 1-800-829-4933 or by checking any tax documents you filed with that number. Keep your EIN in a safe place with your other business records, just as you would your Social Security number.

Do I need an EIN if I'm starting a business but haven't hired anyone yet?

Not necessarily. If you're a sole proprietor operating alone, you can use your Social Security number. However, if you plan to hire employees soon or want to open a business bank account, getting an EIN now will save you a step later.