Quick answer: If your business is in the 50 states or DC, fax Form SS-4 to 855-641-6935 and the IRS faxes your EIN back in about 4 business days. Include a return fax number on the form so they can send it. Different location? See the full routing table below.
Applying for an Employer Identification Number (EIN) does not have to mean weeks of waiting. Faxing Form SS-4 is the middle option between the instant online tool and slow postal mail: you usually get your EIN back by return fax within four business days. Below we cover the exact fax numbers, what to prepare, how to send it, and what to expect afterwards.
EIN and Form SS-4: the basics
An EIN is a unique nine-digit number that works like a Social Security number for a business. The IRS issues it to identify your business for tax purposes, and it stays with the business even if the name or structure changes later. You need one to:
- Open a business bank account
- File business tax returns
- Hire employees
- Apply for business licences
Form SS-4 is the official application you use to get that number. It asks for your business name and address, entity type, the reason you are applying, and the number of employees you expect — along with a valid SSN or ITIN for the responsible party, who must be a real person, not another business.
Three ways to apply: online, fax, or mail
How each method compares on speed and reliability.
| Method | EIN turnaround | Worth knowing |
|---|---|---|
| Online | Immediate | Fastest, but you must finish in one session — it can time out mid-application |
| Fax | About 4 business days | Reliable, no session to lose; EIN returned by fax if you include a return number |
| 4 to 6 weeks | Slowest; use only if fax and online are not options |
The online tool is the quickest when it works, but it has to be completed in a single sitting and will expire if you stop to check something. Faxing avoids that risk: you send the form once, keep your confirmation, and the EIN comes back within a few days.
Before you fax: what to prepare
Accurate information is what keeps the application moving. Before you send anything, have these ready:
- Legal business name plus any trade names or DBAs
- A valid SSN or ITIN for the responsible party (a real person)
- Full business address and principal place of business
- Entity type (LLC, corporation, and so on)
- Date the business started or was acquired
- Reason for applying and expected number of employees over the next 12 months
- Principal business activity
Fill the form in typed text or clear black ink, then double-check the high-risk fields before you send: the business name matches your legal documents, the correct tax classification is marked, the mailing address is valid, the closing month of your accounting year is noted, and every required signature is present. The IRS rejects forms with missing or unreadable information, so a clean, legible form is the single best way to avoid a delay.
How to fax Form SS-4, step by step
- Complete Form SS-4 fully and accurately, and keep the original for your records.
- Add a cover sheet with your business name, contact details, and a return fax number so the IRS can send your EIN back.
- Pick the correct IRS fax number for your location (routing table below).
- Fax the packet — cover sheet first, then the numbered SS-4 pages. Keep scans clean and high-contrast.
- Save the transmission report showing the destination number, timestamp, and page count.
- Wait about 4 business days for the IRS to fax your EIN back.
You do not need a physical fax machine. Municorn Fax lets you fill a PDF or scan a paper SS-4 and send it from your phone or computer, with a timestamped delivery confirmation and no per-page or long-distance charges — which also makes it the simplest option if you are faxing from outside the US.
Where to fax Form SS-4
The fax number depends on where the business (or the responsible individual) is located.
| Your location | Fax number | IRS office |
|---|---|---|
| One of the 50 states or DCMost applicants | 855-641-6935 | EIN Operation, Cincinnati, OH 45999 |
| No legal residence or business in any state — faxing from within the US | 855-215-1627 | EIN International Operation, Cincinnati, OH 45999 |
| No legal residence or business in any state — faxing from outside the US | 304-707-9471 | EIN International Operation, Cincinnati, OH 45999 |
IRS fax numbers can change. These reflect the IRS “Where to File Form SS-4” page as last reviewed on April 28, 2026 — confirm the current number on the day you file.
Applying from outside the US, or without an SSN
The IRS online EIN tool is only for applicants in the US or its territories, and it needs the responsible party to have an SSN or ITIN. If you are forming a US company from abroad and your responsible party has neither, you cannot use the online tool — you apply by fax, phone, or mail instead. Faxing is the usual written route: use the international rows in the table above (855-215-1627 from within the US, 304-707-9471 from outside), and complete the form following the IRS SS-4 instructions. Municorn Fax reaches both numbers with no long-distance charge, which is the simplest option when you are sending from another country.
EIN rejected online? (Reference 101 and other errors)
The online tool runs an automated check and sometimes returns a reference number instead of an EIN. The most common is Reference 101: the IRS found an existing business whose name is too similar to yours. Because the check covers all 50 states, a near-match registered in another state is enough to trigger it. It does not mean your application was denied, or that your state formation is invalid — it means the application needs to be reviewed by a person.
The fix is to file Form SS-4 by fax (or mail) so an IRS employee can review it manually. Fax domestic applications to 855-641-6935, and include a copy of your state formation document — your Articles of Organization or Certificate of Formation — so the agent can confirm your entity is legitimate. You will get your EIN back by fax in about four business days; include a return fax number, as the IRS no longer faxes back an annotated copy of the form. For the full walkthrough — why Reference 101 happens and every way to clear it — see our EIN Reference Number 101 guide.
A few other codes you might see:
- Reference 102: the responsible party’s SSN or ITIN does not match IRS records. Recheck it, and fax the SS-4 if the error persists.
- Reference 105: too many attempts in a short window. Wait 24 hours, then retry online or fax the form.
- One EIN per responsible party, per day — this limit applies across all methods and is a common reason an application stalls.
If you need the number urgently, the IRS Business & Specialty Tax Line (800-829-4933) can sometimes issue an EIN over the phone once your details are verified.
Naming a third-party designee
You can name a third-party designee on the SS-4 to deal with the IRS about the application and answer questions about the form. They need to give their full name, phone number, and fax number on the form, and the authority lasts 60 days from the date the EIN is assigned. Designees are usually tax preparers, business attorneys, accountants, or an authorised business partner.
After you get your EIN
The IRS mails an EIN confirmation notice (CP575) to the address on your Form SS-4, usually within a couple of weeks. Keep it — you will need it later, and if it goes missing the IRS can reissue confirmation as a 147C letter. A few things to line up once your number is assigned:
- Choosing S-corp status? That is a separate election on Form 2553, due about 2 months and 15 days into the tax year — see our guide on how to fax Form 2553 to the IRS.
- LLC tax classification is set when you file: single-member, partnership, or corporation.
- Keep your address current with the IRS so you receive notices and tax documents.
For the fax numbers behind other IRS forms, see our full list of IRS fax numbers.
