The IRS EIN reference number 101 appears when the online EIN Assistant can’t finish your application automatically, almost always because your entity’s name is too close to one already in the IRS database. Your application wasn’t denied. It was pulled out of the automated line so a person can look at it, which means you’ll need to submit Form SS-4 by fax or mail. A faxed application typically produces a new EIN in about four business days.
What Triggers a 101 Error
The most common cause is a name conflict. Your LLC or corporation name may be unique in the state where you formed it, but the IRS database covers all 50 states, and a near-duplicate from anywhere in the country is enough to stop the automated system. The online tool isn’t designed to judge whether two similar names actually belong to different businesses, so it hands the file to a human reviewer instead.
Two other situations can produce the same error code. The IRS issues only one EIN per responsible party per day, across all application channels.1Internal Revenue Service. IRS Publication 1635 – Understanding Your EIN If you already got an EIN for a different entity earlier the same day, wait until tomorrow and try again. And if an EIN already exists for this exact entity, applying again will keep failing. Check for one before you refile.
Check Whether You Already Have an EIN
Before spending four days on a paper application, confirm the number isn’t already sitting in your records. The IRS suggests looking in a few obvious places:
- The original CP 575 confirmation notice the IRS mailed when the EIN was first assigned. This notice is issued only once and cannot be reissued.2Internal Revenue Service. IRS Notice CP 575 B – Notice of Employer Identification Number Assignment
- Your business bank, which has the EIN on file for the account.
- Any state or local agency where you applied for a business license.
- Any prior business tax return you’ve filed.
If nothing surfaces, 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 read it back to you.3Internal Revenue Service. Employer Identification Number
File Form SS-4 by Fax or Mail
Once you’ve ruled out a duplicate, the fix is to download Form SS-4 from IRS.gov and submit it on paper so an agent can process it manually. A few fields cause most of the avoidable delays.
Line 7a and 7b ask for the responsible party’s name and SSN or ITIN. These have to match what the IRS already has on file exactly. Line 9a asks for the entity type, and only one box may be checked. Line 10 asks why you’re applying, with options such as “started new business” or “banking purpose only.” The responsible party, or someone with proper authorization, has to sign and date the form.4Internal Revenue Service. Form SS-4 (Rev. December 2025) – Application for Employer Identification Number
Because a 101 usually comes from a name match, including a copy of your state formation document (articles of incorporation, certificate of organization, or the equivalent) with your fax or letter helps the reviewer confirm your entity is real. The instructions don’t require this attachment, but practitioners report it speeds the review along.
Where to Send It and How Long It Takes
Fax is the faster route. Domestic applicants send Form SS-4 to 855-641-6935, and the IRS faxes back a cover sheet carrying your new EIN in roughly four business days.3Internal Revenue Service. Employer Identification Number Put a return fax number on the application. The IRS no longer sends back an annotated copy of the SS-4 itself.
If you’d rather mail it, the address is:
Internal Revenue Service
Attn: EIN Operation
Cincinnati, OH 45999
Mail takes about four weeks.3Internal Revenue Service. Employer Identification Number The IRS instructions recommend submitting Form SS-4 four to five weeks before you need the EIN, so if a bank account opening or filing deadline is coming up, build in the lead time or use fax.5Internal Revenue Service. Instructions for Form SS-4 (12/2025)
When the application is approved, the IRS mails a CP 575 notice with your assigned EIN. It’s issued once, so store it with your permanent records.2Internal Revenue Service. IRS Notice CP 575 B – Notice of Employer Identification Number Assignment
If Your Business Is Based Outside the United States
The online EIN Assistant isn’t available to applicants whose principal place of business is outside the U.S., regardless of any reference number. If that’s you, the 101 process isn’t what applies. International applicants can apply by phone at 267-941-1099, Monday through Friday, 6 a.m. to 11 p.m. Eastern time.3Internal Revenue Service. Employer Identification Number Form SS-4 can also be faxed to 855-215-1627 from within the U.S. or 304-707-9471 from outside it, or mailed to the same Cincinnati office directed to “Attn: EIN International Operation.”6Internal Revenue Service. Where to File Your Taxes for Form SS-4