Guides
Form SS-4: How to Apply for an EIN
Form SS-4 is the IRS application for an Employer Identification Number (EIN), the 9-digit federal tax ID the IRS assigns to businesses, estates, trusts, and other entities. You can file it four ways: online (EIN issued immediately), by fax (about 4 business days), by mail (about 4 weeks), or by phone for international applicants only. Filing directly with the IRS is free.
An EIN identifies your entity to the IRS the way a Social Security number identifies an individual. You use it to open a business bank account, file employment and business tax returns, and set up payroll. This guide covers who needs one, how each filing method works, the responsible-party rule, and the one-EIN-per-day limit that trips up serial founders.
Who Needs an EIN
Most entities other than single-owner businesses without employees need an EIN. The IRS requires one if you operate as a corporation or partnership, hire employees, file employment or excise tax returns, administer certain trusts, estates, or retirement plans, or withhold taxes on income paid to a non-resident alien. A sole proprietor with no employees can often use their SSN instead.
You generally need an EIN if any of the following apply:
- You formed a corporation, S corporation, or partnership.
- You have (or will hire) employees and must file payroll tax returns such as Form 941.
- You file excise tax returns (for example, alcohol, tobacco, or fuel).
- You administer an estate, trust, or qualified retirement plan.
- You are a single-member LLC that elects corporate taxation or hires employees.
- You changed your entity structure or ownership (for example, incorporating a sole proprietorship or buying an existing business).
A single-member LLC with no employees that is taxed as a disregarded entity may not strictly need an EIN for federal tax filing, but many banks require one to open a business account, so most owners get one anyway.
How to Apply for an EIN: The Four Methods
There are four ways to file Form SS-4, and the method controls how fast you get the number. The online assistant issues the EIN immediately and is the IRS-recommended route for anyone whose principal business is in the United States or a U.S. territory. Fax takes about 4 business days, mail about 4 weeks, and phone is reserved for international applicants.
| Method | Turnaround | Who can use it | Notes |
|---|---|---|---|
| Online (IRS.gov/EIN) | Immediate | Entities with a U.S. or U.S. territory principal place of business; responsible party with SSN or ITIN | Free; must finish in one session |
| Fax (855-641-6935 domestic) | About 4 business days | Domestic and international filers | Include a return fax number to get the EIN faxed back |
| About 4 weeks | Domestic and international filers | Submit 4 to 5 weeks before you need the number | |
| Phone (267-941-1099) | Immediate on the call | International applicants only | Not toll-free; 6 a.m. to 11 p.m. ET, Mon-Fri |
Applying Online (Numbered Steps)
The online EIN Assistant is the fastest route and issues the number on screen the moment you finish. It is available to any applicant whose legal residence, principal place of business, or principal office is in the U.S. or a U.S. territory, and whose responsible party has a valid SSN, ITIN, or EIN.
- Go to IRS.gov/EIN and open the online EIN Assistant. Confirm your principal business is in the U.S. or a U.S. territory.
- Apply during the assistant’s hours: roughly 6 a.m. to 1 a.m. ET Monday through Friday, with shorter windows on weekends. The tool is not available around the clock.
- Select your entity type (LLC, corporation, partnership, estate, trust, sole proprietor, and so on) and the reason you are applying.
- Enter the responsible party’s name and SSN or ITIN, plus the entity’s legal name, mailing address, and start date.
- Answer the questions about employees, excise taxes, and business activity.
- Complete the whole application in one session. The tool cannot save your progress and the session expires after 15 minutes of inactivity.
- Submit. The EIN appears on screen immediately. Download and save the confirmation notice (CP 575) right away, because you cannot retrieve it later online.
Applying by Fax
Fax works for both domestic and international filers and is the fastest non-online option. Complete a paper Form SS-4, sign it, and fax it to the IRS. If you include a return fax number, the IRS generally faxes the assigned EIN back within about 4 business days.
- Download Form SS-4 from IRS.gov and complete every applicable line.
- Fax it to 855-641-6935 (domestic; the 50 states and D.C.) or 855-215-1627 (international filers inside the U.S.).
- Include a return fax number so the IRS can send the EIN back. Without it, expect the number by mail instead, which is slower.
- Wait about 4 business days for the return fax.
Applying by Mail
Mail is the slowest method and suits filers who do not need the EIN quickly. Send the completed Form SS-4 to the IRS address listed in the current instructions for your location. Processing runs about 4 weeks.
- Complete and sign a paper Form SS-4.
- Mail it to the address in the Form SS-4 instructions for domestic or international applicants.
- File 4 to 5 weeks ahead of when you will need the EIN, since processing takes about 4 weeks.
Applying by Phone (International Applicants Only)
Phone application is limited to applicants who have no legal residence, principal place of business, or principal office in the U.S. or its territories. An IRS representative takes the SS-4 information over the call and assigns the EIN during the conversation.
Call 267-941-1099 (not a toll-free number), 6 a.m. to 11 p.m. Eastern time, Monday through Friday. Have a completed Form SS-4 in front of you so you can answer each question, and note that the person on the call must be authorized to receive the EIN.
The Responsible Party Rule
Every EIN application must name a responsible party: the individual who ultimately owns or controls the entity, or who exercises ultimate effective control over it and its funds. Except for government entities, the responsible party must be a natural person, not another company. Nominees and paid preparers cannot be listed as the responsible party.
The IRS defines the responsible party as the person with a level of control over, or entitlement to, the entity’s funds and assets that lets them directly or indirectly control, manage, or direct the entity. In practice this is usually the principal owner, general partner, grantor, or managing member.
The responsible party must supply a taxpayer ID: an SSN or ITIN (or an EIN, only when the responsible party is itself a government entity). You cannot enter “N/A” unless the person is a foreign individual who has no SSN or ITIN and is not eligible for one. If a responsible party changes after the EIN is issued, the entity should report the update to the IRS using Form 8822-B within 60 days.
The One-EIN-Per-Day Limit
The IRS issues only one EIN per responsible party per day. This cap applies across every method (online, fax, mail, and phone), not just the online tool, and it exists to keep issuance equitable and to limit automated abuse.
The limit is tied to the person, not the entity. A founder launching several LLCs at once cannot pull multiple EINs in a single day under their own name as responsible party. For trusts the limit applies to the grantor, owner, or trustor; for estates it applies to the decedent or the debtor.
To get around the daily cap without waiting, an applicant can:
- Space the applications across separate business days, one EIN each day.
- Name a different responsible party for each entity, where that is legally accurate and the person genuinely controls that entity.
- Route additional applications through a different authorized person who qualifies as the responsible party for those specific entities.
Frequently Asked Questions
Is Form SS-4 the same as an EIN?
No. Form SS-4 is the application; the EIN is the 9-digit number the IRS assigns after processing the form. You file the SS-4 to request the number. Once issued, you rarely touch the SS-4 again, though lenders and banks sometimes ask for a copy of the filed form or the IRS confirmation notice (CP 575) to verify your EIN.
How much does it cost to get an EIN?
Nothing, when you apply directly with the IRS. Online, fax, mail, and phone applications are all free. Third-party services may charge a fee to file on your behalf, but the underlying EIN itself carries no IRS charge. Be cautious of sites that imply a government fee exists, because the IRS never charges for issuing an EIN.
How long does it take to get an EIN?
It depends on the method. Online applications issue the EIN immediately on screen. Fax filings generally return the number within about 4 business days if you include a return fax number. Mailed applications take roughly 4 weeks. International phone applicants receive the EIN during the call itself.
Can I get an EIN without a Social Security number?
Yes, in limited cases. The online tool requires the responsible party to have an SSN or ITIN. A foreign responsible party with neither, and who is ineligible for either, can apply by fax, mail, or phone and enter “Foreign” or leave the ID field appropriately marked per the instructions. International applicants without a U.S. business location apply by phone at 267-941-1099.
What is a responsible party on Form SS-4?
The responsible party is the individual who ultimately owns or controls the entity and its funds. Except for government entities, it must be a natural person, not a company, and the person must provide an SSN or ITIN. It is typically the principal owner, general partner, grantor, or managing member. If it changes later, file Form 8822-B within 60 days.
Why was I limited to one EIN per day?
The IRS caps issuance at one EIN per responsible party per day to keep the process fair and curb automated bulk requests. The limit follows the person, not the business, and applies to online, fax, mail, and phone requests alike. To obtain more than one, space applications across business days or use a different, legitimate responsible party for each entity.
Do I need a new EIN if my business changes?
Sometimes. You generally need a new EIN when your entity type or ownership structure changes, for example when a sole proprietorship incorporates, a partnership converts to a corporation, or you take over an existing business as a different entity. Simple changes such as a name or address update do not require a new EIN; report those with Form 8822-B instead.
Related reading: for choosing how your entity is taxed before you apply, see Form 8832 entity classification election and Form 2553 to elect S corporation status. Once you have employees, you will file the employer’s quarterly payroll tax return on Form 941, and if you need more time on a business return, review Form 7004 for a business tax extension. For contractor paperwork, see how to fill out a W-9.
Reviewed by The Ledgerism Editorial Team. Last reviewed: July 2026.