Form SS-4 is the IRS application you use to get an Employer Identification Number (EIN), the nine-digit number the IRS assigns to businesses, nonprofits, trusts, estates, and other entities for tax filing and reporting.1Internal Revenue Service. About Form SS-4, Application for Employer Identification Number (EIN) An EIN functions like a Social Security number for an organization, and the IRS issues one for free through its online portal, by fax, by mail, or, for international applicants, by phone.2Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) – Section: Purpose of Form
Who Has to File Form SS-4
Corporations and partnerships need an EIN whether or not they have employees. Sole proprietors generally need one only if they hire employees, file certain excise tax returns, or set up a retirement plan. Nonprofits, trusts, and estates that report income or handle payroll taxes also need their own EIN.3Internal Revenue Service. Get an Employer Identification Number
Even outside tax filing, an EIN comes up quickly in day-to-day operations. Banks typically require one to open a business checking or savings account, and it is often needed to apply for federal and state licenses and permits.4U.S. Small Business Administration. Get Federal and State Tax ID Numbers If you are forming an LLC, partnership, corporation, or tax-exempt organization, form the entity with your state first, then apply for the EIN.3Internal Revenue Service. Get an Employer Identification Number
What to Have Ready Before You Start
Pull the following together before you open the application. The online version cannot be saved, so you have to finish it in one sitting.3Internal Revenue Service. Get an Employer Identification Number
Entity Information
Enter the legal name of the entity exactly as it appears on the charter, articles of incorporation, or other formation document. If the business operates under a different name, list the “doing business as” (DBA) or trade name on a separate line so the IRS can tie both names to the same account. You will also give the mailing address and physical address (if different), the date the business started or was acquired, and the type of entity, such as a corporation, partnership, LLC, trust, or estate.5Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) – Section: Lines 5a-5b and Line 11
If the entity is an LLC, the form asks for the number of members and how the LLC will be classified for federal tax purposes. An LLC can be treated as a partnership, a corporation, or a disregarded entity depending on its elections. If you plan to elect corporate treatment, check the “Corporation” box and note which form you will file (Form 1120 or 1120-S).6Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) – Section: Lines 8a-8c
The Responsible Party
Every application must name a “responsible party,” meaning the individual who owns, controls, or exercises effective control over the entity and directly or indirectly manages its funds and assets.7Internal Revenue Service. Responsible Parties and Nominees Unless the applicant is a government entity, the responsible party must be a person, not another entity, and must supply a Social Security Number or Individual Taxpayer Identification Number on the application.8Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) – Section: Lines 7a-7b
Access to funds alone is not enough. A minor child who is the beneficiary of a trust, for example, is entitled to the trust’s property but is not authorized to control or manage it, so the child would not qualify as the responsible party.7Internal Revenue Service. Responsible Parties and Nominees
Reason for Applying
You have to check exactly one box for the reason you are applying. Options include starting a new business, hiring employees, and changing the type of organization, among others. Do not leave this section blank.9Internal Revenue Service. Instructions for Form SS-4 (Rev. December 2025) – Section: Line 10
How to Submit Form SS-4
The IRS accepts Form SS-4 four ways, and the method you pick controls how quickly the EIN comes back.
Online
The online EIN application is the fastest route and issues the number immediately on approval. The tool is open Monday through Friday from 6:00 a.m. to 1:00 a.m. (next day), Saturday from 6:00 a.m. to 9:00 p.m., and Sunday from 6:00 p.m. to midnight, all Eastern time. You cannot save your progress, the session expires after 15 minutes of inactivity, and you are limited to one EIN per responsible party per day.3Internal Revenue Service. Get an Employer Identification Number
The online option is available only if the responsible party has a valid SSN or ITIN and the entity’s principal place of business is in the United States or a U.S. territory. Only government entities may apply online using another EIN in place of an SSN or ITIN.3Internal Revenue Service. Get an Employer Identification Number
Fax
If you cannot apply online, fax the signed Form SS-4 and you will generally get the EIN back within four business days. From the 50 states and D.C., the fax number is 855-641-6935. International applicants use 855-215-1627 (from within the U.S.) or 304-707-9471 (from outside).10Internal Revenue Service. Where to File Your Taxes for Form SS-4 Include a return fax number so the IRS can fax the EIN assignment back to you.11Internal Revenue Service. Instructions for Form SS-4 (12/2025)
Mailing works, but it is slow. Processing takes about four to five weeks. Domestic applicants send the signed form to: Internal Revenue Service, Attn: EIN Operation, Cincinnati, OH 45999. International applicants use the same address but direct the form to “Attn: EIN International Operation.”10Internal Revenue Service. Where to File Your Taxes for Form SS-4
Telephone (International Applicants Only)
If you have no legal residence, principal place of business, or principal office in the United States or a U.S. territory, you can apply by calling 267-941-1099 (not toll-free) Monday through Friday, 6:00 a.m. to 11:00 p.m. Eastern time. The caller must be authorized to receive the EIN and answer questions about the application. Fill out Form SS-4 before you call so you have every field ready. The IRS representative will assign your EIN during the call. Write the number on the form, sign and date it, and keep it. If the representative asks, mail or fax the signed form within 24 hours.11Internal Revenue Service. Instructions for Form SS-4 (12/2025)
Naming a Third-Party Designee
If you want an accountant, attorney, or business partner to handle the application for you, name that person as a third-party designee in the signature section of the form. The designee is authorized to answer questions about the completed Form SS-4 and to receive the newly assigned EIN, and that authority ends as soon as the EIN is issued.11Internal Revenue Service. Instructions for Form SS-4 (12/2025) The IRS sends the EIN back to the designee through the same method used to apply (online, fax, or phone), but the official EIN notice is always mailed to the taxpayer.
After the EIN Is Issued
You can start using the EIN right away to open a bank account, apply for licenses, and file tax returns.12Internal Revenue Service. Employer Identification Number – Section: When You Can Use Your EIN The IRS will also mail a confirmation notice (CP 575) to the address on your application. Keep it. Banks and other institutions sometimes ask for it as proof of the EIN, and the IRS does not reissue it.
If the notice is lost, request a verification letter (called a 147C letter) by calling 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. You can also find the number on past tax returns, bank records, or any state or local license applications where you previously used it.13Internal Revenue Service. Employer Identification Number
When You Need a New EIN Later
An EIN stays with the entity for the life of the business. Changing your name or address does not require a new one. Changing ownership or structure usually does, and the specific triggers depend on your entity type.14Internal Revenue Service. When to Get a New EIN
- Sole proprietors need a new EIN when incorporating, forming a partnership, or declaring bankruptcy.
- Corporations need a new EIN when receiving a new charter from the secretary of state, becoming a subsidiary, converting to a partnership or sole proprietorship, or merging to create a new corporation.
- Partnerships need a new EIN when incorporating, dissolving so one partner continues as a sole proprietor, or ending one partnership and starting a new one.
- LLCs need a new EIN when terminating an existing LLC and forming a new corporation or partnership, or when a single-member LLC must file excise or employment tax returns.
- Estates need a new EIN when creating a trust with estate funds or when the estate operates a sole proprietorship after the owner’s death.
- Trusts need a new EIN when converting between trust types, for instance when a revocable trust becomes irrevocable, or a living trust converts to a testamentary trust.
If your situation falls into any of these, you file a fresh Form SS-4 through the same channels described above.14Internal Revenue Service. When to Get a New EIN