What a Business Tax ID Number Is and When You Need One

A Business Tax ID Number Is Your Business's Social Security Number for the IRS

A Business Tax ID Number, officially called an Employer Identification Number (EIN), is a nine-digit number the IRS assigns to identify your business for tax purposes. The format is XX-XXXXXXX. If you operate as a sole proprietor with no employees, you can use your personal Social Security Number instead — but most business structures need an EIN to file taxes, open a business bank account, or hire staff.

The IRS issues EINs free of charge. You do not pay to get one, and you do not renew it — once assigned, your EIN stays with your business for life, even if the business changes ownership or structure. The number ties your business to tax records, payroll filings, and any liability you report to the government.

Think of it this way: your Social Security Number identifies you personally to the IRS. Your EIN identifies your business as a separate entity. If you are self-employed and work alone, the IRS may let you use your SSN. If you have employees, a partnership, a corporation, or an LLC, you need an EIN.

Key Takeaways

An EIN is a nine-digit number the IRS assigns to your business at no cost, and you use it on tax forms, payroll filings, and bank accounts.
Sole proprietors with no employees can use their Social Security Number instead of an EIN, but most other business structures require one.
You can request an EIN online through the IRS website, by phone, by mail, or by fax — online is fastest and gives you the number when ready.
Once the IRS assigns your EIN, it does not change or expire, even if your business structure or ownership changes.
You need an EIN before you hire your first employee, open a business bank account, or file certain tax forms like Form 1065 or Form 1120.

Who Needs an EIN

The IRS requires an EIN if your business is organized as a corporation, S corporation, partnership, LLC, or nonprofit. You also need one if you operate as a sole proprietor but have employees on your payroll. If you are self-employed and work alone with no staff, you can file taxes using your Social Security Number — but many sole proprietors still get an EIN to keep their personal and business finances separate.

Some businesses need an EIN even without employees. If you operate a farm, run a business that generates over $600 in annual income from a single client, or manage a trust or estate, the IRS may require an EIN. If you plan to open a business bank account, most banks will ask for an EIN or your SSN — having an EIN makes the process clearer and protects your personal credit from business debt.

Seasonal businesses, nonprofits, and businesses with foreign owners all need EINs. If you are unsure whether your situation requires one, the IRS website has a worksheet that walks through the rules for your specific business type.

How to Request an EIN from the IRS

The fastest way to get an EIN is online through the IRS website at irs.gov. You fill out Form SS-4 (process for Employer Identification Number) on the IRS's online system, and the IRS assigns your number when ready. You can print your confirmation letter right away and use the number the same day. This method works if you are a U.S. citizen or resident alien with a valid Social Security Number or Individual Taxpayer Identification Number (ITIN).

If you cannot file online, you can request an EIN by phone by calling the IRS at 1-800-829-4933. The phone line is open Monday through Friday, 7 a.m. to 10 p.m. Eastern Time. You will speak to an IRS representative who will ask questions about your business and issue the number over the phone. You can also mail or fax Form SS-4 to the IRS, though this method takes two to four weeks.

Before you request an EIN, gather basic information: your business name, the type of business structure (sole proprietor, LLC, corporation, etc.), the reason you need the EIN (hiring employees, opening a bank account, etc.), and the date you started or plan to start the business. If you have a business address, have that ready too. The entire process takes less than 15 minutes online.

What Information the IRS Asks For

Form SS-4 asks for your legal name, the business name (if different), your address, and your Social Security Number or ITIN. You will also state your business structure — sole proprietor, partnership, S corporation, C corporation, LLC, or nonprofit. The IRS asks when your business started or will start, what type of work you do, and how many employees you have or plan to hire.

You will also indicate the reason you are requesting an EIN: opening a bank account, hiring employees, changing business structure, or filing a tax return. If you are a foreign national, the IRS will ask for your country of citizenship and may request an ITIN instead of using your SSN. None of this information is difficult to provide — most people complete the form in under 10 minutes.

The IRS does not verify your information in real time, so make sure what you enter is accurate. If you make a mistake on the form, you can request a new EIN, but it is simpler to get it right the first time.

Using Your EIN on Tax Forms and Bank Accounts

Once you have an EIN, you use it on nearly every business tax form you file. If you have employees, you report their wages and payroll taxes on Form 941 (Employer's Quarterly Federal Tax Return) using your EIN. If you operate as a partnership, you file Form 1065 (U.S. Return of Partnership Income) with your EIN. Corporations file Form 1120 (U.S. Corporation Income Tax Return) with their EIN. Even sole proprietors who get an EIN use it on Schedule C (Profit or Loss from Business) if they file separately from their personal return.

When you open a business bank account, the bank will ask for your EIN or SSN. Providing your EIN instead of your personal Social Security Number keeps your business finances separate from your personal credit and makes it harder for the bank to mix the two. This separation also protects you if your business faces debt or legal trouble — creditors can pursue the business but not your personal assets (depending on your business structure).

Your EIN also appears on W-2 forms you issue to employees, 1099 forms you send to contractors, and any business licenses or permits you hold. It is the single identifier that ties all your business tax records together.

Common Mistakes When Getting or Using an EIN

One common mistake is requesting an EIN before you actually need one. If you request an EIN but never use it, the IRS may flag it as inactive. If you later use that same EIN for a different business, the IRS can get confused about which business the tax filings belong to. Request your EIN only when you are ready to use it — when you are about to hire your first employee, open a business account, or file your first business tax return.

Another mistake is confusing your EIN with your business license number or state tax ID. These are different. Your EIN is federal and issued by the IRS. Your state may issue a separate business tax ID or sales tax permit. You need both if your state requires them, and they serve different purposes. Do not assume one number works for all government filings.

Some people also lose track of their EIN or forget which number belongs to which business. Keep your EIN confirmation letter in a safe place — you will need it to file taxes, open accounts, and respond to IRS notices. If you cannot find it, you can call the IRS at 1-800-829-4933 and they will look it up for you using your business name and address.

What Happens If You Do Not Have an EIN When You Need One

If you are required to have an EIN but do not, the IRS can assess penalties. If you hire employees without an EIN, you cannot file payroll tax forms correctly, and the IRS will not know which business the wages belong to. This can trigger an audit and penalties for late or incorrect payroll reporting. If you operate as a corporation or partnership without an EIN, your tax return will be rejected.

Banks also will not open a business account without an EIN or SSN. If you try to use your personal Social Security Number for a business account and the bank suspects you are running a business, they may freeze the account or ask you to convert it to a business account with an EIN. This can delay your access to funds and create confusion about which account is personal and which is business.

The good news is that getting an EIN is free and takes minutes online. If you realize you need one, you can request it when ready and use it right away. There is no penalty for getting an EIN late as long as you get it before you file your first business tax return or hire your first employee.

Frequently Asked Questions

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

Yes, if you are a sole proprietor with no employees, you can use your SSN on your tax return instead of an EIN. However, many sole proprietors still get an EIN to keep business and personal finances separate. Banks and vendors may also prefer an EIN because it clearly identifies the business rather than mixing it with your personal credit.

How long does it take to get an EIN?

Online requests are processed when ready — you receive your EIN number on screen and can print your confirmation letter right away. Phone requests take a few minutes during the call. Mail and fax requests take two to four weeks. If you need an EIN quickly, explore online or call the IRS.

Do I need a separate EIN for each business I own?

Yes. Each business entity needs its own EIN. If you own two separate businesses, you request two separate EINs. If you own multiple locations of the same business under the same legal entity, you use one EIN for all locations.

What if I change my business structure from sole proprietor to an LLC?

If you change your business structure, you may need a new EIN. The IRS treats different structures as different entities for tax purposes. Consult a tax professional or the IRS to confirm whether your specific change requires a new EIN or whether you can keep the existing one.

Can someone else request an EIN on behalf of my business?

Yes. A business representative, accountant, attorney, or authorized person can request an EIN on your behalf by mail, fax, or phone. Online requests must be made by someone with a valid SSN or ITIN, so if you are a foreign national, you may need to use mail, fax, or phone instead.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.