By Sarah Martinez · Published March 15, 2026 · Updated April 10, 2026 · 8 min read
The IRS EIN fax number for domestic applicants is 855-641-6935. Fax your completed Form SS-4 to that number, include a return fax number on your cover sheet, and the IRS will fax your Employer Identification Number back within approximately 4 business days.
If you have an international address or are faxing from outside the U.S., different numbers apply — covered below. This guide walks through every fax number, the exact 8-step process for submitting Form SS-4, what to include on your cover sheet, key fields on the form, and the mistakes most likely to delay your EIN.
Fastest Option
The IRS online EIN tool at irs.gov/EIN issues your EIN immediately — no waiting. If your responsible party has a U.S. SSN, ITIN, or EIN and you have a U.S. address, online is faster. Use fax when you can't access the online tool or when you're an international applicant.
IRS EIN Fax Numbers: Quick Reference
The correct fax number depends on where your business is located — not which state within the U.S., just domestic vs. international.
| Applicant Type | Fax Number | Notes |
|---|---|---|
| Domestic (U.S. address) | 855-641-6935 | All 50 states + D.C. |
| International (faxing from within U.S.) | 855-215-1627 | U.S. territories, no U.S. business address |
| International (faxing from outside U.S.) | 304-707-9471 | Not toll-free |
All SS-4 fax submissions route to the IRS Cincinnati, OH processing center. The fax line accepts transmissions 24/7, though processing happens on business days only.
Phone Is for International Applicants Only
Domestic applicants can no longer request an EIN by phone. If you have a U.S. address and can't use the online tool, fax or mail are your only options. International applicants can call 267-941-1099 (Monday–Friday, 6 a.m.–11 p.m. ET) to receive their EIN during the call.
Who Should Apply for an EIN by Fax
Most U.S.-based businesses should use the online tool — it's instant and free. Faxing makes sense when:
- Your responsible party already obtained an EIN online and cannot use the online tool again that day (one EIN per responsible party per day)
- You have a non-U.S. address and want faster processing than mail
- You're applying on behalf of a trust, estate, or entity with a complex structure that you'd prefer to review offline before submitting
- You want a paper record of the exact form submitted (fax confirmation page + copy of the SS-4)
Fax is not appropriate if you need your EIN same-day — use the online tool for that.
Step-by-Step: How to Fax Form SS-4 to the IRS
Download Form SS-4
Get the current version of Form SS-4 from irs.gov/FormSS4. The most recent revision is December 2025. Using an outdated version can result in delays or rejection.
Complete All Required Fields
Fill in every applicable field. Use black ink if handwriting — print clearly. If using a PDF editor, use a standard font (Arial or Times New Roman). Leave no required fields blank. See the Key Fields section below for the most critical lines.
Sign and Date the Form
The responsible party listed on Line 7a must sign. The signature must match the name exactly as written on the form. An unsigned SS-4 will not be processed.
Prepare a Cover Sheet
This is the most overlooked step. Your cover sheet must include:
- Your business name
- Full contact information
- Your return fax number — the IRS will fax your EIN to this number. Without it, the IRS cannot return your EIN by fax.
Use our free IRS fax cover sheet to ensure you include every required field.
Number All Pages
Sequentially number every page of the fax: cover sheet (page 1), Form SS-4 (page 2), and any supporting documents. This helps the IRS process your package as a complete submission.
Fax to the Correct Number
Based on your location:
- Domestic applicants: 855-641-6935
- International (from U.S.): 855-215-1627
- International (from outside U.S.): 304-707-9471
You can fax from a physical machine, a library or UPS store, or an online fax service. mFax.to lets you fax Form SS-4 directly from your phone — upload your completed PDF, enter the IRS fax number, and send.
Save Your Transmission Confirmation
Your fax confirmation page — showing the number dialed, timestamp, and success status — is your only proof of delivery. The IRS does not send fax acknowledgments. Save this immediately.
Wait for the IRS Fax Back
Within approximately 4 business days, the IRS will fax a cover page with your EIN to the return fax number you provided. A CP-575 confirmation letter will also arrive by mail at your business address within 4–6 weeks.
After Receiving Your EIN
Wait at least 2 weeks after receiving your EIN before using it for e-filing or making electronic tax deposits. The IRS needs time to fully activate the number in its systems.
What to Put on Your Fax Cover Sheet
A missing or incomplete cover sheet is the most common reason applicants don't receive their EIN back. Include all of the following:
- To: Internal Revenue Service, EIN Operation
- Fax number: 855-641-6935 (or your applicable number)
- From: Your full business name
- Your fax number: The number where the IRS should fax your EIN — this is mandatory
- Your phone number: In case the IRS needs to reach you by phone
- Date: Today's date
- Number of pages: Total pages including the cover sheet
- Brief note: "Enclosed: Form SS-4, EIN Application. Please fax EIN to the number above."
The IRS fax cover sheet article has a template you can use directly.
Key Fields on Form SS-4
Form SS-4 has 18 lines. These are the ones that most often cause errors or delays:
| Line | Field | Common Error |
|---|---|---|
| 1 | Legal business name | Must match your state registration exactly — punctuation and "Inc./LLC" included |
| 7a–7b | Responsible party name + SSN/ITIN/EIN | Must be an individual (not the entity itself); their SSN or ITIN is required |
| 8a–8c | LLC details | Many LLCs incorrectly leave these blank or choose the wrong tax classification |
| 9a | Entity type | Sole proprietors, LLCs, and S-Corps are often confused here |
| 10 | Reason for applying | Must select one — "Started new business" is not always correct |
| 16–17 | Principal business activity | Vague entries like "services" cause processing delays; be specific |
Responsible Party Must Be an Individual
Line 7a must list a real person — not the LLC or corporation. Government entities are the only exception. If the responsible party doesn't have an SSN or ITIN, they must apply for one before the entity can get an EIN.
Fax vs. Other EIN Application Methods
| Method | Speed | Who Can Use | Notes |
|---|---|---|---|
| Online (irs.gov/EIN) | Immediate | U.S. applicants only; responsible party needs SSN/ITIN/EIN | Recommended by the IRS; session expires in 15 min |
| Fax (Form SS-4) | ~4 business days | All applicants | Must include return fax number on cover sheet |
| Phone | Same call | International applicants only | Call 267-941-1099, Mon–Fri, 6 a.m.–11 p.m. ET |
| Mail (Form SS-4) | ~4 weeks | All applicants | Domestic: Cincinnati, OH 45999; slowest option |
The IRS explicitly recommends the online method for eligible applicants, calling it out in the December 2025 revision of the SS-4 instructions. If you qualify for online, use it. If not, fax is the right next choice.
What Happens After You Fax?
Once your Form SS-4 reaches the IRS:
- IRS receives and queues your fax — typically the same business day
- IRS agent reviews the form — verifying required fields, entity type, responsible party
- EIN is assigned — within approximately 4 business days
- IRS faxes your EIN — to the return fax number on your cover sheet; a single confirmation page is sent
- CP-575 letter mailed — the official EIN confirmation letter mails to your business address within 4–6 weeks regardless of application method
If the IRS finds an error on your form, they will contact you by phone (using the number from your cover sheet) or by letter. In that case, correct the identified issue and resubmit.
Using EIN on Tax Returns Before CP-575 Arrives
If you need to file a return or make a deposit before your CP-575 arrives, write "Applied For" in the EIN field, along with the date of application. Never use your SSN as a substitute for a pending EIN.
Common Mistakes That Delay Your EIN
These are the ten mistakes most likely to cause a delay or rejection:
- No return fax number on the cover sheet — the IRS can't send your EIN back
- Legal name mismatch — the name on Line 1 doesn't match your state registration documents
- Wrong fax number — using the domestic number for an international application
- Unsigned form — the responsible party must sign; signature must match Line 7a
- Wrong responsible party — listing the LLC or corporation instead of an individual
- Incomplete entity type — choosing the wrong option on Line 9a (common for LLCs)
- Vague business description — "services" or "consulting" on Line 17 triggers manual review
- Outdated form version — always use the December 2025 revision from irs.gov
- Re-faxing before confirming non-receipt — duplicate submissions create duplicate EIN records
- Applying before forming the entity — the IRS recommends registering your business with your state first
For the mechanics of sending the fax itself — file preparation, resolution settings, multi-page faxes — see our guide on how to fax a PDF document.
What If You Don't Receive Your EIN After 4 Business Days?
Follow these steps in order:
- Check your fax confirmation page — verify the correct number was dialed and the transmission showed "success"
- Confirm your return fax number is active and can receive incoming faxes
- Call the IRS Business & Specialty Tax Line: 1-800-829-4933 — available Monday–Friday, 7 a.m.–7 p.m. local time; have your SS-4 details and confirmation page ready
- Be aware of backlog delays — during high-volume periods (tax season, fiscal year-ends), fax processing can extend beyond 4 business days
- Do not re-fax unless the IRS confirms they never received your original — resubmitting creates duplicate records
If you're experiencing significant financial hardship caused by the delay, contact the Taxpayer Advocate Service at 1-877-777-4778. They can escalate cases involving genuine economic harm.
Need Your EIN Application Sent from Your Phone?
If you're faxing Form SS-4 remotely — from home, on the road, or without a physical fax machine — mFax.to handles the entire process from your iPhone or Android. Upload your completed SS-4 PDF, type in the IRS fax number (855-641-6935 for domestic), and send. You'll receive a delivery confirmation immediately, which serves as your proof of transmission.
Over 5 million users have sent faxes through mFax — including tax forms, IRS correspondence, and legal documents. It costs far less per page than a UPS Store or library fax, and you have the confirmation receipt the moment it sends.
For a full walkthrough of the IRS faxing process across all form types, see our complete guide to faxing the IRS.