If the online EIN Assistant stopped your application with IRS EIN reference number 101, the automated system has flagged a conflict it can’t resolve on its own, almost always because your entity’s name is too close to one already in the IRS database. Your application wasn’t denied. To finish getting your EIN, you submit Form SS-4 so an IRS employee can review it manually, and a faxed application typically produces a new EIN in about four business days.
What Triggers Reference Number 101
The most common cause is a name match. Your LLC or corporation name may be unique in the state where you formed it, but the IRS database pulls from all 50 states, and a near-duplicate from another state is enough to stop the online process. The system isn’t built to decide whether your entity is legitimately new or a duplicate, so it hands the file to a human instead.
A second trigger has nothing to do with your name. The IRS issues only one EIN per responsible party per day, across all application methods.1Internal Revenue Service. IRS Publication 1635 – Understanding Your EIN If you already pulled an EIN for a different entity earlier the same day, wait until the next business day and try again.
A third possibility: an EIN already exists for this exact entity, and the system is refusing to issue a second one. Reapplying won’t change that outcome, so rule it out before filing anything new.
Check Whether You Already Have an EIN
Before refiling, look in the obvious places:
- The CP 575 notice the IRS mailed when the EIN was originally assigned. The IRS issues this notice only once and will not generate a duplicate.2Internal Revenue Service. IRS Notice CP 575 B – Notice of Employer Identification Number Assignment
- The bank where you opened a business account.
- Any state or local agency where you applied for a business license.
- Prior business tax returns.
If none of those turn it up, call the IRS Business and Specialty Tax Line at 800-829-4933, Monday through Friday, 7 a.m. to 7 p.m. local time. After verifying your identity, an agent can look up any EIN tied to your SSN or ITIN and give it to you over the phone.3Internal Revenue Service. Employer Identification Number
Fix It by Filing Form SS-4
Once you’ve confirmed you don’t already have an EIN, download Form SS-4 from IRS.gov and complete it on paper. A few fields matter more than others when you’re clearing a 101.
Line 7a and 7b ask for the responsible party’s name and SSN or ITIN; these need to match exactly what the IRS has on file. Line 9a asks for your entity type, and only one box can be checked. Line 10 asks why you’re applying. The form must be signed and dated by the responsible party or someone with proper authorization.4Internal Revenue Service. Form SS-4 (Rev. December 2025) – Application for Employer Identification Number
Because 101 usually involves a name conflict, include a copy of your state formation document (articles of incorporation, certificate of organization, or the equivalent) when you fax or mail the form. The instructions don’t technically require it, but practitioners consistently report that it speeds up the manual review.
Where to Send Form SS-4 and How Long It Takes
Faxing is faster. Domestic applicants send Form SS-4 to 855-641-6935, and the IRS faxes back a cover sheet with your new EIN in about four business days.3Internal Revenue Service. Employer Identification Number Include a return fax number on your application; the IRS no longer returns an annotated copy of the SS-4 itself.
To mail the form instead, send it to:
Internal Revenue Service
Attn: EIN Operation
Cincinnati, OH 45999
Mailed applications take roughly four weeks.3Internal Revenue Service. Employer Identification Number IRS instructions recommend completing the form at least four to five weeks before you need the number, so build in time if you’re waiting on a bank account or a filing deadline.5Internal Revenue Service. Instructions for Form SS-4 (12/2025)
After approval, the IRS mails a CP 575 notice confirming the EIN. It’s issued only once and will not be replaced, so file it with your permanent records.2Internal Revenue Service. IRS Notice CP 575 B – Notice of Employer Identification Number Assignment
If Your Principal Business Is Outside the U.S.
The online EIN Assistant isn’t available to international applicants at all, so a 101 isn’t really your scenario. International applicants apply by phone at 267-941-1099, Monday through Friday, 6 a.m. to 11 p.m. Eastern.3Internal Revenue Service. Employer Identification Number You can also fax Form SS-4 to 855-215-1627 from within the U.S. or 304-707-9471 from outside it, or mail it to the Cincinnati address directed to “Attn: EIN International Operation.”6Internal Revenue Service. Where to File Your Taxes for Form SS-4