A business tax ID number is a nine-digit code the IRS assigns to identify your business for federal tax purposes, and the standard version, the Employer Identification Number (EIN), is free to get directly from the IRS. Most applicants finish the online application in a single sitting and receive the number immediately.1Internal Revenue Service. Get an Employer Identification Number
What an EIN Is
The EIN is the federal tax ID for businesses in the United States. It follows a nine-digit format written as XX-XXXXXXX, and the IRS also calls it a “federal tax identification number.”2Internal Revenue Service. Taxpayer Identification Numbers (TIN) It gives your business a tax identity separate from your personal one, which keeps the two sets of records distinct.
Sole proprietors with no employees and no excise tax filings can use their Social Security number in place of an EIN. Many still choose to get one so their SSN doesn’t end up on W-9s, invoices, and other paperwork shared with clients and vendors.
When You Need One
The IRS groups the triggers into two buckets: what you do, and what you are. On the activity side, you need an EIN if you hire employees, pay excise taxes, or withhold taxes on non-wage income paid to a nonresident alien.3Internal Revenue Service. Employer Identification Number Hiring even one employee is the most common trigger, since payroll withholding and wage reporting are impossible without one.4Internal Revenue Service. Businesses With Employees
On the entity side, you need an EIN if you operate any of the following:
- Partnership
- LLC
- Corporation
- Tax-exempt organization
- Estate or trust (except certain grantor-owned revocable trusts)
- Retirement plan or IRA
- Farmers’ cooperative
The retirement plan line catches some self-employed people by surprise. Set up a solo 401(k) and the plan itself needs its own EIN.3Internal Revenue Service. Employer Identification Number
Beyond the legal requirements, banks routinely ask for an EIN before opening a business account, and you’ll need it to apply for business licenses or to file a business tax return by mail.3Internal Revenue Service. Employer Identification Number Businesses dealing in alcohol, tobacco, or firearms must have one to file the excise returns those products require.
What to Have Ready Before You Apply
Gather this information before you start. It’s the same data the online tool asks for and the same data that goes on paper Form SS-4.5Internal Revenue Service. Instructions for Form SS-4 (12/2025)
- Legal name of the business, exactly as it appears on your formation documents.
- Physical business address (not a P.O. box).
- The responsible party: the individual who owns or ultimately controls the entity and its funds. This must be a real person, not another business entity, unless you’re a government agency. Nominees who don’t actually control the entity cannot be listed.6Internal Revenue Service. Responsible Parties and Nominees
- The responsible party’s SSN or ITIN, matching IRS records exactly.
- Entity type: corporation, partnership, LLC, sole proprietorship, trust, and so on.
- Reason for applying, such as starting a new business, hiring employees, or opening a bank account.
How to Apply
Online
The IRS online EIN tool is the fastest option. It’s free, and the number is issued immediately at the end of the session. To use it, your principal place of business must be in the United States or a U.S. territory, and the responsible party must have an SSN or ITIN, not an EIN. Only one EIN per responsible party is allowed per day through the online system, so setting up several entities at once takes several days.1Internal Revenue Service. Get an Employer Identification Number
The tool’s hours (Eastern Time):
- Monday through Friday: 6:00 a.m. to 1:00 a.m.
- Saturday: 6:00 a.m. to 9:00 p.m.
- Sunday: 6:00 p.m. to midnight
By Fax or Mail
Complete a paper Form SS-4 and send it in. Domestic applicants can fax it to 855-641-6935 and typically receive the EIN within four business days. Mailing the form to IRS, Attn: EIN Operation, Cincinnati, OH 45999, takes about four weeks, and the IRS recommends sending it four to five weeks before you actually need the number.5Internal Revenue Service. Instructions for Form SS-4 (12/2025)
International Applicants
If your principal place of business is outside the United States, the online tool isn’t available to you. Apply by phone, fax, or mail using Form SS-4. The international phone line is 267-941-1099 (not toll-free). Phone applications are reserved for international applicants; domestic businesses can’t apply that way.1Internal Revenue Service. Get an Employer Identification Number
The Application Is Free
The IRS charges nothing for an EIN, ever. Third-party sites that charge a fee are filling out the same free form on your behalf. The IRS puts it plainly: “Beware of websites that charge for an EIN. You never have to pay a fee for an EIN.”1Internal Revenue Service. Get an Employer Identification Number If a site is asking for your credit card, close the tab and go to IRS.gov directly.
When a Business Change Forces a New EIN
An EIN isn’t permanent through every business change. The general rule: a change in ownership or entity structure requires a new EIN, while a simple name or address change does not.7Internal Revenue Service. When to Get a New EIN A sole proprietor who incorporates, for example, has created a new legal entity in the IRS’s eyes, and that corporation needs its own number. The same logic applies when a partnership incorporates, a corporation is created through a merger, or an LLC terminates and reforms as a corporation or partnership.
If You Lose or Need to Update Your EIN
If you can’t find your EIN, check the confirmation notice the IRS sent when you first applied, look at a previous business tax return, or contact the bank that holds your business account. If those don’t turn it up, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7:00 a.m. to 7:00 p.m. local time. After verifying your identity, an agent can give you the number by phone or send Letter 147C confirming it.3Internal Revenue Service. Employer Identification Number
When the person controlling the business changes, you must notify the IRS within 60 days using Form 8822-B. The same form updates a business address, though address-only changes are voluntary. Processing takes four to six weeks.8Internal Revenue Service. Form 8822-B Change of Address or Responsible Party – Business
State Tax IDs Are Separate
A federal EIN doesn’t cover state tax obligations. Whether you also need a state tax ID depends on your state’s income tax and employment tax rules.9U.S. Small Business Administration. Get Federal and State Tax ID Numbers If your state has an income tax, you’ll almost certainly need one. If you hire employees, most states require separate registration for state unemployment insurance. Businesses selling taxable goods or services typically need a state sales tax permit with its own number. The federal EIN is often a prerequisite for state registration, so get it first, then check with your state’s department of revenue for the rest.