What Is an SS-4 Form and How Do You Get an EIN: Filing and Next Steps

To get an Employer Identification Number, file Form SS-4 with the IRS. The application is free, and the fastest route is the IRS Online EIN Assistant, which issues the number at the end of the session. Fax takes about four business days; mail takes four to five weeks. Foreign applicants can apply by phone.¹

Do You Actually Need an EIN

Corporations, partnerships, trusts, estates, and most LLCs need their own EIN for federal tax filing and reporting.² Certain events also trigger the requirement even if you’ve been operating without one: hiring your first employee, establishing a retirement plan, acquiring an existing business, or changing your business structure.³

Restructuring is worth flagging. A sole proprietorship that incorporates or becomes a partnership cannot keep using the old EIN. The IRS treats the restructured entity as a new taxpayer and expects a new number.³

Sole Proprietors and Single-Member LLCs

A sole proprietor with no employees and no excise tax obligations can use a personal Social Security Number instead of an EIN. Many still get one to avoid handing out an SSN to clients and vendors.

Single-member LLCs are the point where people get tripped up. A single-member LLC treated as a disregarded entity does not need its own EIN if it has no employees and no excise tax liability; the owner’s SSN or existing EIN covers federal income tax reporting. Once the LLC hires anyone or picks up excise tax obligations, it must get its own EIN and use that number for employment taxes. In practice most new single-member LLCs get one anyway, because banks typically require it to open a business account and some states require it for licensing.⁴

What to Have Ready Before You Start

The online form times out after 15 minutes of inactivity and cannot be saved mid-session, so gather everything first.¹ You’ll need:

The entity’s legal name exactly as it appears on the charter, articles of organization, or the applicant’s Social Security card.⁵
Any trade or DBA name that differs from the legal name (Line 2).
The responsible party’s name and SSN or ITIN. This must be an individual who controls or manages the entity, not another business, unless the applicant is a government agency. For publicly traded entities, that means the principal officer of a corporation or a general partner of a partnership.³
The entity type from Line 9a (sole proprietorship, corporation, partnership, personal service corporation, estate, nonprofit, and other categories).
The reason for applying on Line 10, such as starting a new business, hiring employees, purchasing an existing business, or changing the organization type.⁵
Your principal business activity and line of business (Lines 16 and 17), plus the date wages were first paid or will be paid if you’ll have employees.⁵

How to File Form SS-4

Online

The IRS Online EIN Assistant walks through each question and assigns the number at the end of the session.¹ Your principal place of business must be in the United States or a U.S. territory; foreign entities incorporated outside the U.S. cannot apply online.⁶

The tool isn’t available around the clock. Eastern time hours are Monday through Friday, 6 a.m. to 1 a.m. the next day; Saturday, 6 a.m. to 9 p.m.; and Sunday, 6 p.m. to midnight. The IRS limits you to one EIN application per responsible party per day, so stagger your filings if you’re forming multiple entities.¹

Fax

Download Form SS-4 from IRS.gov, fill it out, and fax the completed form. Expect the EIN back in about four business days.³ The number depends on where the business is located:

Domestic applicants (50 states and D.C.): 855-641-6935
International applicants faxing from within the U.S.: 855-215-1627
International applicants faxing from outside the U.S.: 304-707-9471⁷

Mail

Mail the completed SS-4 to Internal Revenue Service, Attn: EIN Operation, Cincinnati, OH 45999. International applicants use the same address with “EIN International Operation” in the attention line. Processing runs four to five weeks.⁷

Phone for International Applicants

If your principal place of business is outside the United States, call 267-941-1099, Monday through Friday, 6 a.m. to 11 p.m. Eastern time. It is not a toll-free number.⁸

Using a Third-Party Designee

To let someone else handle the application, complete the third-party designee section on Line 18 and sign the form. The designee’s authority ends the moment the EIN is assigned. If the designee’s address or phone number matches the taxpayer’s, the application has to go in by mail or fax rather than online or phone.³

After the EIN Is Assigned

Online applicants see the number on-screen at the end of the session and should print the confirmation page before closing the browser. However you applied, the IRS mails a formal confirmation called the CP 575 notice to the address on record. Keep it. Banks, state agencies, and lenders ask for it as proof of your EIN, and getting a replacement takes extra steps.¹

An EIN is permanent. Even if you close the business, the IRS never reassigns that number to another entity.⁹

Reporting Changes Later

If the responsible party or business address changes after the EIN is assigned, notify the IRS within 60 days by filing Form 8822-B. Address and responsible-party updates typically take four to six weeks to process.¹⁰ Missing the 60-day window doesn’t trigger a specific penalty, but outdated records can delay tax correspondence and create problems during audits.

Closing the Account

An EIN can’t be deleted, but you can close the associated business tax account. Send a letter to Internal Revenue Service, Cincinnati, OH 45999 that includes the legal name of the business, the EIN, the business address, and the reason for closing, and enclose a copy of the CP 575 notice if you still have it. The IRS won’t close the account until all required returns are filed and any outstanding taxes are paid.¹¹

Retrieving a Lost EIN

Before calling the IRS, look at the original CP 575 notice, past business tax returns, state or local license applications, and records from the bank where the business account is held. If none of those work, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7 a.m. to 7 p.m. local time (Pacific time for Alaska and Hawaii). The agent will verify your identity and provide the number over the phone.⁸

The IRS Doesn’t Charge a Fee

Applying for an EIN through the IRS is free, regardless of method.¹ Third-party sites that look official and charge anywhere from $50 to several hundred dollars are not affiliated with the agency. If you’ve already paid one, the IRS recommends disputing the charge with your bank or credit card company and reporting the site to the Federal Trade Commission.¹² Starting directly at IRS.gov avoids the problem.

1
Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. About Form SS-4, Application for Employer Identification Number (EIN)
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Internal Revenue Service. Instructions for Form SS-4 (12/2025) – Application for Employer Identification Number (EIN)
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Internal Revenue Service. Single Member Limited Liability Companies
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Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025)
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IRS.gov. EIN Individual Request – Online Application
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Internal Revenue Service. Where to File Your Taxes for Form SS-4
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Internal Revenue Service. Employer Identification Number
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Internal Revenue Service. If You No Longer Need Your EIN
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IRS. Form 8822-B, Change of Address or Responsible Party – Business
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Internal Revenue Service. Closing a Business
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Internal Revenue Service. Report Fake IRS, Treasury or Tax-Related Emails and Messages