Form SS-4, Application for Employer Identification Number, is the IRS form you use to get an EIN, the 9-digit number (for example 12-3456789) given to sole proprietors, corporations, partnerships, estates, trusts and other entities. As of October 2026, applicants in the U.S. can apply online free of charge and use the EIN straight away, fax applications are generally answered within 4 business days, and mailed ones take about 4 weeks.
The online application asks the same questions as the paper Form SS-4, so knowing the form helps either way. These are the points from the IRS's December 2025 instructions that decide how quickly you get your number and whether you get the right one. For the bigger picture on when a small business needs one, see our guide to getting an EIN.
Four ways to apply
| Method | Who can use it | When you get the EIN |
|---|---|---|
| Online | Applicants in the United States or U.S. territories | At the end of the session, and you can use it immediately |
| Fax (Fax-TIN) | Any applicant | Generally within 4 business days |
| Any applicant | Approximately 4 weeks | |
| Telephone | International applicants only | During the call |
The IRS no longer issues EINs by telephone for domestic taxpayers. If you have no legal residence, principal place of business or principal office in the U.S. or its territories, you can call 267-941-1099 (not a toll-free number), 6:00 a.m. to 11:00 p.m. Eastern time, Monday to Friday.
For the online route, the principal officer, general partner, grantor, owner or trustor must have a valid SSN, EIN or ITIN. If that's your blocker, our ITIN guide covers the alternative number.
The one EIN per day rule
EIN issuances are limited to one per responsible party, per day, whether you apply online, by phone, fax or mail. For trusts the limit applies to the grantor, owner or trustor, and for estates to the decedent or debtor. If you're setting up several companies, plan the applications over several days.
Who the responsible party is
The responsible party is the person who ultimately owns or controls the entity, or who exercises ultimate effective control over it. That person should have enough control over, or entitlement to, the entity's funds or assets to control, manage or direct it. For a company whose shares trade on a public exchange, the responsible party is the principal officer for a corporation.
If the responsible party changes later, you don't apply again: you report it on Form 8822-B, which also covers address and location changes.
Lines people get wrong
- Line 9a, entity type for an LLC. A single-member LLC treated as a disregarded entity ticks "Other" and writes "disregarded entity". A multi-member LLC that accepts partnership treatment ticks "Partnership". An LLC electing corporation or S corporation status ticks "Corporation" and writes the return it will file, Form 1120 or 1120-S.
- Reason for applying. Don't apply if you already have an EIN and are only hiring employees.
- Employees expected. Give the highest number of employees expected in the next 12 months, and if none are expected, skip line 14.
- Line 14, Form 944. If you expect employment tax of $1,000 or less in a full calendar year, you can tick this box to file Form 944 once a year instead of Form 941 each quarter. Once ticked, you keep filing Form 944 until the IRS tells you to switch. That figure is as of October 2026.
- First date wages were paid. Enter N/A if you don't plan to have employees.
- Third Party Designee. Complete it only if you want the named person to receive the EIN and answer questions about the form.
The line 14 choice catches new employers out: tick it and you file Form 944 annually, leave it and you file Form 941 every quarter.
When you need a new EIN
A sole proprietorship that incorporates or enters into a partnership needs a new EIN. A disregarded single-member LLC is treated as part of its owner for income tax, with income and expenses on the owner's return (for example Schedule C), but it still uses its own name and EIN for employment taxes, certain excise taxes, and Form 5472 if it's wholly owned by a foreign person.
An EIN is for business activities only. The instructions are clear that you shouldn't use it in place of your Social Security number or ITIN.
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How to complete Form SS-4
- Decide your entity type and tax classification before you start, because line 9a follows from it.
- Identify the responsible party and have their SSN, ITIN or EIN ready.
- Choose your method: online if you're in the U.S., fax if you can't apply online and need it within days, mail if you can wait about 4 weeks.
- Answer the employee questions honestly, including the Form 944 box.
- Sign it. If an IRS representative asks for the signed form during a phone application, it must be mailed or faxed within 24 hours.
- Save the EIN assignment notice. Online applicants can view, print and save it at the end of the session.
The verdict
If you're in the U.S., apply online: it's free, you get the number on the spot and the paper form only slows you down. Get line 9a and the responsible party right first, because a wrong entity type is the mistake that's hardest to unwind later, and remember the one-per-day limit if you're forming more than one company.
Frequently asked questions
What is Form SS-4 used for?
To apply for an employer identification number (EIN), the 9-digit number the IRS assigns to businesses, estates, trusts and other entities.
How long does it take to get an EIN with Form SS-4?
Online applicants in the U.S. get it immediately. Fax applications are generally answered within 4 business days, and mail takes approximately 4 weeks.
Can I apply for an EIN by phone?
Only if you're an international applicant with no legal residence, principal place of business or office in the U.S. or its territories.
How many EINs can I get in a day?
One per responsible party, per day, whatever method you use.
Does an LLC need Form SS-4?
Yes, to get its own EIN. A single-member LLC treated as a disregarded entity ticks Other on line 9a and writes disregarded entity.
Is there a fee for an EIN?
No. The IRS says applicants in the U.S. and its territories can apply for and receive an EIN free of charge on IRS.gov.
