How to Apply for a Federal Identification Number

To apply for a Federal Identification Number — the IRS’s Employer Identification Number, or EIN — complete Form SS-4 and submit it directly to the IRS at no cost. The fastest route is the online EIN Assistant at irs.gov, which issues the nine-digit number immediately if your principal place of business is in the United States or a U.S. territory.¹ Fax takes about four business days, mail takes roughly four weeks, and phone is reserved for international applicants.

You need an EIN if you operate as a corporation, partnership, or multi-member LLC, hire employees, withhold tax on payments to non-resident aliens, or file employment or excise tax returns. Estates, trusts, tax-exempt organizations, and retirement plans need one too.¹ A sole proprietor with no employees can legally file under a Social Security Number, but many still apply so they can open a business bank account and keep their SSN off invoices and contracts.

What to Gather Before You Start

The application uses IRS Form SS-4. If you apply online, you cannot save your progress, and the session times out after 15 minutes of inactivity, forcing you to start over.² Collect everything first.

The entity’s full legal name, exactly as it appears on your formation documents.
Entity type: sole proprietorship, partnership, corporation, LLC, estate, trust, or other.
Your reason for applying: starting a business, hiring employees, opening a bank account, or changing structure.
The responsible party’s name and Social Security Number or ITIN.
Physical street address and mailing address if different.
Date the business started or was acquired.
A short description of your principal business activity.
The number of employees you expect to hire in the next 12 months, including zero.³

Who the Responsible Party Is

Every application must name a responsible party, and it must be a human being, not another entity. The only exception is government agencies.⁴ This is the person who owns, controls, or exercises effective control over the entity and manages its funds. For a corporation, that’s usually the principal officer. For a partnership, the general partner. For a trust, the grantor. For an estate, the executor. You’ll enter that person’s SSN or ITIN on the form.⁵

The Four Ways to File

Which method you use depends on where the entity is based and how fast you need the number.

Online

If your principal place of business or legal residence is in the U.S. or a U.S. territory, use the EIN Assistant at irs.gov. The number is issued immediately once you finish a valid application.¹ The tool is open Monday through Friday from 6:00 a.m. to 1:00 a.m. Eastern, Saturday from 6:00 a.m. to 9:00 p.m. Eastern, and Sunday from 6:00 p.m. to midnight Eastern.⁶

Fax

Domestic applicants fax a completed Form SS-4 to 855-641-6935.⁷ Include a return fax number. The IRS typically faxes the EIN back within four business days.¹ International applicants fax 855-215-1627 from within the U.S. or 304-707-9471 from outside the country.

Mail

Mail the completed form to Internal Revenue Service, Attn: EIN Operation, Cincinnati, OH 45999.⁷ Processing takes about four weeks.³ International applicants use the same Cincinnati address but write “Attn: EIN International Operation.”

Phone (International Only)

If your principal place of business is outside the United States, call 267-941-1099 Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern.¹ An IRS representative walks through the Form SS-4 questions and assigns the EIN on the call. The number is not toll-free.

If Someone Else Applies for You

To let an accountant or attorney file on your behalf, complete the third-party designee section on Line 18 of Form SS-4 and sign the form.⁸ Their authority ends the moment the EIN is assigned. If the designee’s address or phone number matches yours, the application has to go in by mail or fax rather than online or phone.

It Costs Nothing — Watch for Imposter Sites

Getting an EIN from the IRS is free through every channel.⁶ An industry of lookalike websites charges up to $300 to submit the same free application. The FTC has warned that these sites copy IRS logos and formatting, place “IRS” in their domain names, and call their tools “EIN Assistant,” which is the actual name of the IRS’s free tool.⁹ The FTC said fees are often buried in fine print and the sites fail to disclose that they are not affiliated with the government. If a site asks for a credit card during an EIN application, you are not on irs.gov.

Using Your EIN After It’s Issued

The EIN is good for most purposes the moment you receive it. You can give it to your bank, put it on invoices, and file paper tax returns right away. There is roughly a two-week delay before the number fully propagates through the IRS’s electronic systems. During that window you cannot e-file a return, make electronic tax payments, or pass the IRS’s Taxpayer Identification Number Matching Program.¹ If you are setting up payroll, build that lag into your timeline.

The IRS mails a CP 575 confirmation notice to the address on your application. Keep it. If you lose it, 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) and ask for Letter 147C, which verifies the EIN previously assigned to you.¹

If Your Application Gets Rejected

The IRS limits each responsible party to one EIN per day across all methods.¹ Setting up several entities? Spread the applications across consecutive days.

The most common online rejection is a mismatch between the responsible party’s name and their SSN or ITIN. Enter the name exactly as the Social Security Administration has it, including hyphens, suffixes, and middle names. If the online system keeps rejecting a valid entry, file Form SS-4 by fax or mail, where a human reviewer can sort out the discrepancy. Business name conflicts can trigger the same manual-review path: if the IRS flags your entity name as too similar to an existing one, you may be prompted to submit by fax or mail. Temporary technical issues usually clear within 24 hours.

For problems you cannot resolve, call the Business and Specialty Tax Line at 800-829-4933, Monday through Friday from 7:00 a.m. to 7:00 p.m. your local time, with your Form SS-4 information in front of you.¹⁰

A Few Things the EIN Doesn’t Cover

An EIN is permanent and stays with the entity even after the business closes.¹¹ Certain structural changes, however, require a brand-new EIN rather than reuse of the old one — a sole proprietor who incorporates, a corporation that receives a new charter from the secretary of state, a partnership that incorporates, and an LLC that terminates and forms a new entity, among others.¹² Routine changes like a new address, a name change, or adding a partner generally do not.

If the responsible party changes after your EIN is issued, you must notify the IRS within 60 days using Form 8822-B. The same form reports a new business address.¹³ This step is easy to miss when ownership shifts, and skipping it means IRS correspondence about the entity’s taxes goes to the wrong person.

1
Internal Revenue Service. Employer Identification Number
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Taxpayer Advocate Service. When Taxpayers Struggle to Obtain an EIN, Everyone Loses
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IRS. Instructions for Form SS-4 (Rev. December 2025)
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Internal Revenue Service. Responsible Parties and Nominees
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Internal Revenue Service. Form SS-4 – Application for Employer Identification Number
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Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. Where to File Your Taxes for Form SS-4
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Internal Revenue Service. Instructions for Form SS-4
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Federal Trade Commission. FTC Warns Operators of Websites that Charge for an Employer Identification Number and Claim Affiliation with the IRS
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Internal Revenue Service. Telephone Assistance Contacts for Business Customers
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Internal Revenue Service. If You No Longer Need Your EIN
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Internal Revenue Service. When to Get a New EIN
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Internal Revenue Service. About Form 8822-B, Change of Address or Responsible Party – Business