What Is an SS-4 Form? How to Apply for an EIN

The SS-4 form is the IRS application you file to get an Employer Identification Number, the nine-digit tax ID assigned to businesses, trusts, estates, nonprofits, and other entities. Filing directly with the IRS is free, and if you apply online you receive the number at the end of the session.¹ An EIN functions like a Social Security number for your organization, identifying it on tax returns, payroll filings, and bank accounts.

Who Has to File One

Not every business owner needs an EIN. A sole proprietor with no employees who doesn’t file excise tax returns can keep using a personal Social Security number. You need to file Form SS-4 once any of the following applies:²

You hire employees and have to report payroll taxes.
You operate as a partnership or corporation, even without employees.³
You owe excise taxes.
You administer a trust or estate that reports its own income.
You run a nonprofit, church, or club.³
You maintain a qualified retirement plan, including a plan set up by a self-employed person.

Household employers have their own thresholds. If you pay a nanny, housekeeper, or other household worker $3,000 or more in cash wages during 2026, you owe Social Security and Medicare taxes and need an EIN to file Schedule H with your personal return. Paying $1,000 or more in cash wages in any calendar quarter also requires an EIN because it triggers federal unemployment tax.⁴

Banks add a practical reason. Most require an EIN to open a business checking account even for entity types the IRS doesn’t require one from, and they’ll usually ask for your formation documents, ownership agreement, and any applicable licenses alongside it.⁵

What You’ll Need Before You Start

Download the current version of Form SS-4 from irs.gov. It was last revised in December 2025.³ Have this information ready:

The responsible party’s name and taxpayer identification number. This is the person who owns or controls the entity and manages its funds, typically a principal officer for a corporation or a general partner for a partnership.⁶
The entity’s exact legal name as it appears on your organizing documents.
Entity type: sole proprietorship, partnership, corporation, trust, estate, church, nonprofit, or other.
A physical mailing address for IRS notices.
Reason for applying, such as starting a new business, hiring employees, or creating a trust.
The highest number of employees you expect over the next 12 months, split into agricultural, household, and other.
The closing month of your accounting year.
The date you started or acquired the business, or the date the trust was funded.

If you want an accountant or attorney to receive the EIN on your behalf, complete the Third Party Designee section. That authority ends the moment the number is assigned and released; it does not extend to future tax matters, and the official EIN notice always goes to the taxpayer.⁷

How to File and How Long Each Method Takes

Filing is free through every IRS channel. Be cautious of third-party websites that charge for what the IRS provides at no cost.²

Online

The online application at IRS.gov/EIN is the fastest option if your principal place of business is in the United States or a U.S. territory and the responsible party has a valid SSN, EIN, or ITIN. You receive the number at the end of the session and can view, print, and save the assignment notice on the spot.⁷ The system runs Monday through Friday, 6:00 a.m. to 1:00 a.m. Eastern; Saturday, 6:00 a.m. to 9:00 p.m. Eastern; and Sunday, 6:00 p.m. to midnight Eastern. Only one EIN per responsible party per day is allowed.²

Fax

Fax the completed form and expect an EIN back by fax within about four business days. Domestic applicants fax to 855-641-6935. Applicants in U.S. territories or international applicants faxing from within the U.S. use 855-215-1627, and international applicants faxing from outside the U.S. use 304-707-9471.⁷

Mail

Mailed applications take about four weeks. Send the signed form to:⁸

Internal Revenue Service
Attn: EIN Operation
Cincinnati, OH 45999

Applicants with no principal place of business in any state address the envelope to “Attn: EIN International Operation” at the same Cincinnati address.

Phone (International Applicants Only)

If your principal place of business is outside the United States, you can apply by phone at 267-941-1099, Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern.⁹ Domestic applicants cannot use this option.

After You Get Your EIN

The IRS mails a CP 575 notice as the official written confirmation of your new number, showing your entity name, address, and the tax forms you’re expected to file.¹⁰ Keep it. You may need it years later to verify the number.

Even if the number is issued instantly, it can take up to two weeks to become part of the IRS’s permanent records. Until it does, you cannot file an electronic return, make an electronic payment, or pass the IRS Taxpayer Identification Number matching program.¹¹ If a filing or payment falls inside that window, use a paper return.

If you later misplace the number, check the CP 575 notice, your bank, any past business tax return, or any state or local agency where you applied for a license.⁹ If none of those work, call the IRS Business and Specialty Tax Line at 800-829-4933 (TTY 800-829-4059), Monday through Friday, 7:00 a.m. to 7:00 p.m. local time. The IRS will provide the number over the phone after verifying that the caller is authorized to receive it.

When You Need a New EIN

Changing your business name or address does not require a new EIN. In general, you only need a new one when your entity’s ownership or structure changes.¹² Common triggers:

A sole proprietor incorporates, forms a partnership, or declares bankruptcy.
A corporation receives a new charter from the secretary of state, converts to a partnership or sole proprietorship, or merges into a new corporation. Electing S corporation status or surviving a merger does not require a new EIN.
A partnership incorporates, one partner takes over as a sole proprietor, or the partnership ends and a new one begins.
An LLC terminates and becomes a new corporation or partnership, or a single-member LLC picks up excise or employment tax obligations. Converting a partnership to an LLC classified as a partnership does not.
A revocable trust becomes irrevocable, or an estate takes over a sole proprietorship from the deceased owner.

If your situation is unclear, the Business and Specialty Tax Line at 800-829-4933 can tell you which way it falls.⁹

Keeping Your EIN Information Current

If the responsible party changes or your business moves, file Form 8822-B (Change of Address or Responsible Party – Business) within 60 days.⁶

Business name changes work differently by entity type. Corporations and partnerships can check the name-change box on their annual return (Form 1120 or Form 1065); if the current year’s return is already filed, send a signed letter to the IRS at the address where you filed. Sole proprietors notify the IRS by letter signed by the owner or an authorized representative.¹³ Some name changes do require a new EIN; IRS Publication 1635 helps you decide.

To close the business, send a letter to the Cincinnati address asking the IRS to close your EIN account. Include the entity’s legal name, EIN, business address, reason for closing, and a copy of the CP 575 notice if you still have it. The account will not close until all required returns are filed and all taxes owed are paid.¹⁴

1
Internal Revenue Service. About Form SS-4, Application for Employer Identification Number (EIN)
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Internal Revenue Service. Get an Employer Identification Number
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Internal Revenue Service. Form SS-4 Application for Employer Identification Number
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Internal Revenue Service. Publication 926 Household Employer’s Tax Guide (2026)
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U.S. Small Business Administration. Open a Business Bank Account
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Internal Revenue Service. Responsible Parties and Nominees
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Internal Revenue Service. Instructions for Form SS-4 (12/2025)
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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. 21.7.13 Assigning Employer Identification Numbers (EINs)
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Taxpayer Advocate Service. TAS Tax Tip: Employer Identification Numbers
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Internal Revenue Service. When to Get a New EIN
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Internal Revenue Service. Business Name Change
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Internal Revenue Service. Closing a Business