Form SS-4SS-4
Application for an Employer Identification Number (EIN) — the tax number a business, estate or trust needs.
Edition 12/2025
Version last read from the agency on September 28, 2026
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About Form SS-4
Who fills it in
Use Form SS-4 to apply for an employer identification number (EIN): a 9-digit number for employers, sole proprietors, corporations, partnerships, estates, trusts and other entities.
Where it goes
If your business is in the United States or its territories, you can apply online at IRS.gov/EIN and use the number immediately. You can also fax the form (the EIN generally comes back within 4 business days) or mail it.
When
Applying by mail? Send the form at least 4 to 5 weeks before you need the EIN.
Watch out for
- Use only one method for each entity so you don’t end up with more than one EIN.
- A sole proprietor generally needs only one EIN, however many businesses or trade names they operate.
- Report a change of responsible party to the IRS within 60 days, on Form 8822-B.
Read from the agency’s pages on October 8, 2026: IRS — About Form SS-4 · IRS — Instructions for Form SS-4
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