Who signs Form SS-4—and what may a Third Party Designee do?

Who may sign Form SS-4?

The current IRS instructions identify the signer by applicant type. Use the category that matches the entity shown on the application:

• Individual applicant: the individual signs the application.
• Corporation: the president, vice president or another principal officer signs.
• Partnership, government entity or other unincorporated organization: a responsible and duly authorized member or officer with knowledge of the entity’s affairs signs.
• Trust or estate: the fiduciary signs.

The instructions also state that a foreign applicant may have a duly authorized person, such as a division manager, sign. That language is not permission for an unrelated preparer to sign without authority. Preserve the document or internal record establishing who authorized the signer and in what capacity.

What the signature certifies

The signature appears below a declaration that the signer examined the application and believes it to be true, correct and complete. The form also asks for the signer’s printed name and title, the date, and applicant telephone and fax numbers.

Review the entire application before signing. A correct signature does not cure an inaccurate legal name, an ineligible line 7b entry, a conflicting member count or an invented reason for applying. Keep a copy of the final signed version—not an earlier worksheet or unsigned draft—with the transmission record.

What a Third Party Designee is authorized to do

Complete the optional section only when the applicant wants the named individual to receive the entity’s newly assigned EIN and answer IRS questions about the completion of Form SS-4. The form requests the designee’s name, address, ZIP code, telephone number and fax number.

The IRS instructions say the designee’s authority ends when the EIN is assigned and released to that person. This is not continuing authority to manage the business tax account, receive every future notice, change the responsible party or represent the entity in unrelated tax matters.

The signature makes the designee authorization valid

The Form SS-4 instructions state that the signature area must be completed for the Third Party Designee authorization to be valid. Current IRS processing guidance distinguishes application processing from disclosure: when the designee section is completed but the taxpayer did not sign, the IRS may assign the EIN but does not disclose it to the designee.

The May 2026 IRS procedural update also states that an electronic signature is not accepted to authorize third-party disclosure and that a handwritten signature is required for that authorization. That rule should not be broadened into a claim about every IRS form or every signature purpose; it is the current processing instruction for disclosure to the Form SS-4 designee.

A special routing rule when contact details match

The current instructions say that if the third-party designee’s address or telephone number matches the taxpayer’s address or telephone number, the application must be mailed or faxed. Do not assume that the international phone process will disregard this condition.

Matching details can occur when a service provider supplies its own address or phone information throughout the form. Recheck whose address belongs on lines 4a–5b, whose phone belongs in the applicant area, and whose contact data belongs in the optional designee section. Those fields document different parties.

Authorization for an international phone application

The international telephone route requires more than the IRS location test. The principal business must also have been created or organized outside the United States and U.S. territories. A foreign-owned LLC organized in Delaware, Wyoming or another U.S. state is treated as domestic for phone processing and must use another application method.

For an eligible foreign-organized applicant, the person calling must be authorized to receive the EIN and answer questions concerning Form SS-4. Completing the form before calling gives the representative one consistent set of facts.

When the responsible party calls personally, the optional designee section is not needed merely to authorize that same responsible party. When another person calls, complete the Third Party Designee section and signature area correctly. Authentication and valid authority still control whether the IRS can disclose the number.

If the IRS representative asks for the signed form, the December 2025 instructions say to mail or fax it—including the third-party authorization—within 24 hours to the destination provided by that representative. If an EIN is given during the call, write it in the upper-right corner of the retained Form SS-4, sign and date the form, and keep it permanently.

How the EIN reaches an authorized designee

The instructions state that EINs are released to authorized Third Party Designees through the method used to obtain the number: online, telephone or fax. The EIN notice itself is mailed to the taxpayer. For a fax application, provide a reliable return-fax number and retain the IRS response securely.

The designee should deliver the number and response record to the applicant through a secure channel. An EIN is not a secret equivalent to an SSN, but the application and IRS correspondence contain business and personal identifying information that should not be posted publicly or sent through an unverified support channel.

Pre-submission authorization checklist

1. Confirm the applicant entity and its responsible party.
2. Identify the signer’s title and actual authority for that entity type.
3. Print the signer’s name and title clearly, then sign and date the final form.
4. Leave the designee section blank unless a named person genuinely needs the limited authority.
5. If using a designee, verify the name, mailing address, telephone and return-fax details.
6. Check whether matching taxpayer and designee contact details require fax or mail submission.
7. Give the authorized caller the final form and supporting entity facts.
8. Store the signed application, authorization and IRS response together.

Frequent role mistakes

• Naming a formation service as responsible party merely because it filed state papers.
• Assuming the person who transmits the fax is automatically authorized to receive the EIN.
• Signing an unfinished draft and changing material answers afterward.
• Using the designee authority as if it continued for later IRS account matters.
• Sending the application without preserving the version that was actually signed.