How to Apply for an EIN by Fax: SS-4 Fax Numbers, What to Send, What Comes Back

Which fax number to use

The IRS sorts SS-4 faxes by location, not by citizenship: the legal residence of an individual, or the principal place of business or principal office of an entity.

Checked against IRS.gov on November 1, 2026. The SS-4 instructions say the numbers may change without notice, so check the IRS page in the sources before you send.

So a foreign owner whose LLC has its principal place of business in a US state is on the first row, and an applicant with no residence, business or office in any state is on the second. These numbers take EIN applications only: the instructions say Fax-TIN numbers can only be used to apply for an EIN. A Form 2553 S corporation election has its own fax numbers.

Who applies by fax

The IRS recommends applying online where possible, so fax is mostly for the applications the online system cannot take:

• The responsible party has no SSN or ITIN. The online application needs one. On the SS-4, line 7b then says “foreign” or N/A, and the instructions add that an entry is required. The no-SSN guide covers that applicant in full.
• The principal place of business is outside the United States. The IRS sends these applicants to phone, fax or mail.
• The online application refused the name. A reference number such as 101 means the online system could not resolve a conflict with an existing record. A faxed SS-4 is worked by an IRS employee instead.
• A designee shares the applicant’s address or phone. The SS-4 instructions say that application must be mailed or faxed.
• The online application is closed. The fax line never is, though the IRS counts its processing time in business days. The live hours tool shows whether the online route is open right now.

What to send

1. The current Form SS-4 (Rev. December 2025), with every line answered. The instructions say to enter N/A on lines that do not apply, and several lines (1, 7b, 10, 16 and 17) must not be left empty. The line by line SS-4 guide covers every entity type, and there is a filled-in sample for a single-member LLC.
2. A return fax number. The form has a box for the applicant’s fax number beside the signature, and another for a designee’s. The instructions put it plainly: be sure to provide your fax number so the IRS can fax the EIN back to you.
3. The signature block. Name and title, signature and date. If a third party is named as designee, the authorization is valid only with the signature area completed, and the IRS manual requires that signature to be handwritten (more on that below).
4. Nothing else is required by the instructions. The IRS manual says proof that an LLC or corporation is registered with the state is requested only when its research points to a possible duplicate or a same-name entity in the same state. If the online application has already turned you away over the name, that is the situation, and including the state filing saves a round trip.

What comes back, and when

The IRS faxes back a cover sheet with the EIN. It no longer returns your SS-4 with the number written on it, which is what older guides describe.

The IRS currently reports that it processes faxed SS-4 applications 10 business days after receipt (IRS Processing Status for Tax Forms, updated October 2, 2026). The reply then has to be sent back to you, so allow about 11 business days, sometimes longer when the IRS fax queue is busy. That is the figure we plan the faxes we file around, and the timeline guide compares fax with the online and mail routes.

• No return fax number on the form: the IRS manual says the confirmation letter takes about two weeks to arrive by mail instead.
• A designee applied: the EIN goes to the designee by fax, and the SS-4 instructions say the EIN notice is mailed to the taxpayer.
• Using the number: the IRS manual says a new EIN can be used to make a payment or file a return straight away, but is not available for name and TIN matching or other electronic uses for about two weeks. A bank or payment platform that cannot verify a brand new EIN is usually hitting that gap.

When nothing comes back

Call; do not fax it again

If nothing has come back after about 11 business days, call: the IRS manual says a caller can have the EIN confirmed by phone. Call 800-829-4933, Monday to Friday, 7 a.m. to 7 p.m. your local time, with the legal name, the responsible party’s details and the date you faxed. A second fax is the wrong fix: the IRS issues one EIN per responsible party per day by any method, and its instructions say to use only one method for each entity so you don’t receive more than one EIN. The phone guide has what to have ready.

An “EIN problem” fax instead of an EIN

If the SS-4 is missing something the IRS needs, the manual tells examiners to fax back an “EIN problem” cover sheet to the return number, or to mail Letter 45C when there is no return number. Answer what it asks for. Starting a new application instead risks the duplicate the IRS is trying to avoid.

The usual reasons a fax goes unanswered

• The return number on the form cannot receive faxes, was mistyped, or was left off.
• Lines left blank that the instructions say need an entry.
• A designee section signed electronically or with a stamp (next section).
• The pages did not all go through. Keep the fax confirmation report; it is your proof of the date you sent it.

Third-party designees and the signature rule

Anyone faxing an SS-4 for someone else, an accountant, a lawyer or a filing service, does it as the third-party designee named on the form. The SS-4 instructions say the section authorizes that person to answer questions about the form and receive the new EIN, that the authority ends when the EIN is assigned and released to the designee, and that the EIN notice is still mailed to the taxpayer.

The IRS manual adds three requirements. The authorization needs a date, a title and a handwritten signature; an electronic signature is not accepted. The IRS must receive it within 120 days of that date. And when the authorization is incomplete or invalid, for example stamped or signed electronically, the IRS processes the application but does not release the EIN to the designee, so the number reaches the owner only through the mail. The designee’s authority also does not stretch to asking for the letter again later: the manual says a previously assigned EIN is not faxed back to a designee.

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