An EIN and a federal tax ID are not the same thing, though the terms are often used interchangeably

An EIN (Employer Identification Number) is a nine-digit number issued by the IRS that identifies a business entity for tax purposes. A federal tax ID is a broader category that includes an EIN, but also includes your Social Security Number (SSN) if you are a sole proprietor or single-member LLC filing taxes as an individual. The IRS uses whichever number applies to your business structure to track your tax account.

If you are self-employed and file taxes under your Social Security Number, your SSN is your federal tax ID. If you have formed a business entity — a partnership, corporation, LLC, or nonprofit — you need an EIN, which then becomes your federal tax ID for that business. The confusion arises because people often say "federal tax ID" when they mean "EIN," but the reverse is not true: an EIN is always a federal tax ID, but a federal tax ID is not always an EIN.

Key Takeaways

  • An EIN is a nine-digit number for business entities; a federal tax ID is the umbrella term that includes both EINs and Social Security Numbers used for tax purposes.
  • Sole proprietors without employees can use their Social Security Number as their federal tax ID and do not need an EIN unless they hire staff or form an LLC.
  • Partnerships, corporations, LLCs, and nonprofits must obtain an EIN from the IRS before opening a business bank account or filing certain tax forms.
  • You can request an EIN for free from the IRS by phone, mail, fax, or online; the online process is the fastest route and provides your number when ready.

When you need an EIN instead of just your Social Security Number

The IRS requires an EIN if your business is structured as a partnership, S corporation, C corporation, or nonprofit organization. You also need an EIN if you are a sole proprietor who hires employees, even one part-time worker. If you have formed an LLC, you need an EIN unless you are the sole owner and have chosen to be taxed as a sole proprietor (and have no employees).

Many banks will not open a business account without an EIN, even if the law does not technically require one. This is because banks use the EIN to verify your business identity and report interest earned on the account to the IRS. If you plan to separate your personal and business finances — which is standard practice — you will need an EIN to do so.

How to get an EIN from the IRS

The fastest way to obtain an EIN is to explore online through the IRS website at irs.gov. The online process takes about 15 minutes and provides your EIN when ready upon completion. You will need your Social Security Number, the legal name of your business, the business address, and the business structure (sole proprietor, partnership, corporation, etc.).

If you prefer not to explore online, you can call the IRS Business and Specialty Tax Line at 1-800-829-4933 (Monday through Friday, 7 a.m. to 10 p.m. your local time). A representative will issue your EIN over the phone and mail you a confirmation letter. You can also mail Form SS-4 to the IRS or fax it; by mail, the process takes about four weeks, and by fax, about two weeks. There is no fee for an EIN regardless of which method you choose.

What happens if you use your SSN when you need an EIN

If you operate a business that requires an EIN but use your Social Security Number instead, the IRS will eventually flag the discrepancy. This typically happens when you file a business tax return or when a bank reports interest or other income under your SSN that should be under an EIN.

The IRS may assess penalties for filing under the wrong tax ID, and you may face complications when explore for business loans or credit. Additionally, mixing personal and business income under one SSN makes it harder to track business deductions and can raise audit risk. It is simpler and free to obtain an EIN upfront than to correct the problem later.

EIN vs. SSN on tax forms and bank accounts

When you open a business bank account, the bank will ask for your federal tax ID. If you are a sole proprietor using your SSN, you provide that. If you have an EIN, you provide the EIN. The bank will use whichever number you give to report account activity to the IRS and to you on tax forms like the 1099-INT (interest income).

On your business tax return, you will also use your federal tax ID — again, either your SSN or your EIN depending on your business structure. The IRS matches the number on your return to the income reported by banks, employers, and other third parties. Using the correct number ensures those reports match and reduces the chance of an audit notice.

Common situations where people confuse the two

A sole proprietor with no employees often hears "you need a federal tax ID" and assumes they need an EIN. In reality, their Social Security Number is their federal tax ID for tax purposes, and they do not need an EIN unless they hire someone or decide to form an LLC. This is why the terms are so often mixed up — the phrase "federal tax ID" is technically correct for a sole proprietor, but it does not mean they need to explore for an EIN.

Another common mix-up occurs when a business owner is told they need an "EIN for their LLC." This is true if the LLC has more than one member or if the single member chooses to be taxed as a corporation. However, a single-member LLC that is taxed as a sole proprietorship can use the owner's SSN instead. The requirement depends on the tax election, not just the business structure.

Frequently Asked Questions

Can I use my Social Security Number as my business tax ID forever?

Yes, if you remain a sole proprietor with no employees and do not form an LLC or other business entity. However, most business owners eventually form an LLC or hire staff, at which point an EIN becomes necessary. Using your SSN for business also means business income and deductions appear on your personal tax return, which is simpler for very small operations but less professional if you seek business credit or loans.

Do I need an EIN if I have a business but no employees?

Not necessarily. If you are a sole proprietor with no employees and have not formed an LLC or corporation, you can use your Social Security Number. However, if you have formed an LLC (even a single-member LLC taxed as a sole proprietorship), you may need an EIN depending on your tax election. Check with a tax professional or the IRS if you are unsure about your specific situation.

What if I already have an EIN but want to change my business structure?

You do not need a new EIN just because you change your business structure, as long as the same entity continues to exist. However, if you dissolve the old entity and form a new one, you will need a new EIN for the new entity. The IRS considers a change in structure (such as from sole proprietor to LLC) a continuation of the same business and does not require a new number.

How long does it take to get an EIN?

Online applications provide your EIN when ready. Phone applications also issue the number on the call, with a confirmation letter mailed afterward. Fax applications take about two weeks, and mail applications take about four weeks. If you need the number quickly, explore online or call the IRS Business and Specialty Tax Line.

Can someone else explore for an EIN on behalf of my business?

Yes. A tax professional, accountant, attorney, or authorized representative can explore for an EIN on your behalf. They will need a completed Form SS-4 with your signature or authorization, or they can explore online if you have given them power of attorney. Many accountants include EIN process as part of their business setup service.