What the correspondence means Letter 45C is titled “EIN Application Requested/Received (Form SS-4).” Current IRS processing guidance uses it to request information or explain why an EIN application was not processed. If the application included a usable return-fax number, the IRS may instead send an EIN problem fax cover sheet describing the missing item.

Incomplete, delayed and previously assigned are different states

A routine delay means the IRS may still be working an otherwise processable application. An incomplete application lacks information the IRS needs before it can assign the account correctly. A previously assigned case means IRS research located an EIN for the applicant entity and a new one may not be appropriate.

The Internal Revenue Manual says unprocessed Forms SS-4 include applications with a previously assigned EIN and applications that cannot be processed because required information is missing. The IRS returns or corresponds about those applications to explain why it did not assign a new number. Read the actual reason in your notice; the letter number alone does not identify which fact is at issue.

Why one applicant may receive a letter and another a fax

Current IRS processing instructions distinguish the response channel by whether Form SS-4 supplied a return-fax number. Without one, IRS personnel use Letter 45C to correspond with the responsible party. With one, they may use an EIN problem fax cover sheet to request the missing information.

A third-party designee receives protected information only when the authorization is valid. If it is not valid, the IRS does not redirect the problem request to that person merely because the person prepared or transmitted the form. Keep the entity’s mailing address and return-fax channel accessible after submission.

Common issues in current IRS processing guidance

  • Unreadable application: the form or a necessary entry is illegible, requiring a clear replacement rather than a guess.
  • Legal name problem: line 1 is missing, incomplete or does not support the entity type shown elsewhere.
  • Responsible-party information: lines 7a and 7b are missing, inconsistent or cannot be validated under the applicable IRS procedure.
  • LLC details: line 8a indicates an LLC but the member count on line 8b or related entity information is insufficient.
  • Entity type: line 9a is missing or conflicts with other facts on the application.
  • Reason for applying: line 10 has no selection. The current Form SS-4 instructions require one reason and do not permit “N/A.”
  • Operational or tax dates: lines 11, 12 or 15 are missing when the applicant’s filing or employee facts require them.
  • Daily limit: the same responsible party already received an EIN that business day. The IRS applies the one-EIN-per-day limit across online, phone, fax and mail methods.

This list is not a diagnosis of a particular letter. IRS processing tables have entity-specific exceptions and sometimes allow personnel to resolve a missing entry from other consistent information on the form. The selective paragraph or problem-fax language sent to the applicant controls the response needed.

When the IRS asks for state formation evidence

Current processing guidance addresses situations in which IRS research finds an existing EIN for an LLC or corporation with the same primary name in the same state, while the new application shows a different address or responsible party. The IRS may ask for a dated certificate of organization or state filing receipt before processing the request.

That request is designed to distinguish a newly formed legal entity from an address or responsible-party change for an existing entity. Do not form a conclusion from the shared name alone. Provide only the evidence requested and use the IRS procedures for updating an existing account when the entity is in fact the same.

How to build a controlled response

  1. Authenticate the correspondence. Confirm that the letter or fax identifies the correct entity and came through an IRS channel. Do not send personal identifiers to an unverified email or support contact.
  2. Preserve the complete request. Scan or photograph every page, including the date, reference information, selective paragraphs and return instructions.
  3. Identify each requested correction. Make a line-by-line list rather than correcting only the first visible issue.
  4. Rebuild from primary evidence. Use state formation documents, the responsible party’s real details and the current official Form SS-4 instructions. Do not copy a different entity’s sample.
  5. Respond through the method stated by the IRS. Include the notice or reference material the instructions request and keep proof of fax or mail delivery.
  6. Retain one case record. Store the original application, correspondence, corrected form, supporting documents and transmission evidence together.
Do not create a second track The Form SS-4 instructions tell applicants to use only one method for each entity so they do not receive more than one EIN. A request for missing information is a reason to resolve the existing case—not to start simultaneous phone, fax and mail applications.

If the IRS indicates that an EIN already exists

Stop treating the issue as a blank first-time application. Line 18 asks whether the applicant entity shown on line 1 previously applied for and received an EIN. If IRS research located one, an authorized requester can use the agency’s verification procedures. The original CP575 assignment notice is not recreated, but Letter 147C can confirm a previously assigned EIN.

Compare the exact legal entity, not just the owner’s name. An owner may be associated with several entities, each with its own record, while the same entity generally should not receive a replacement EIN merely because its address or responsible party changed.

What the response cannot guarantee

Correcting every requested item makes the application reviewable; it does not promise immediate assignment or a particular response date. IRS inventory, authentication, entity research and the completeness of supporting evidence can affect the result. Track the corrected submission from the IRS received date and use only current official contact guidance for any follow-up.

Official IRS sources See the Instructions for Form SS-4 and IRM 21.7.13, Assigning Employer Identification Numbers. The current IRS procedural updates on Forms SS-4 missing information and Form SS-4 processing provide the 2026 Letter 45C and problem-fax procedures summarized here.