How to fax Form SS-4 to the IRS for an EIN

First, check whether you can apply online

The IRS recommends applying online when you can. Its online application is free, issues the EIN immediately once approved, and is open to entities formed in the United States or a US territory, with their principal place of business there, when the responsible party has a Social Security number or an ITIN. It has to be done in one sitting and times out after 15 minutes of inactivity.

Fax is the route for applicants who can’t use it, for example an entity based outside the United States, or a third-party designee whose address or phone number is the same as the applicant’s, a case the IRS says must be faxed or mailed. Applicants outside the United States and its territories can also apply by phone.

Applying for an EIN is always free: the IRS warns against websites that charge for one. With FaxTonic you pay only for the fax.

Where to fax Form SS-4

The IRS takes faxes on these lines around the clock, but its manual says a fax that reaches the EIN unit after 1 p.m. Eastern time counts as received the next business day.

The return fax line, and why to leave it blank

The SS-4 asks for your fax number so the IRS can fax the EIN back, which it says takes about four business days. FaxTonic sends faxes but can’t receive them, so a FaxTonic number can’t be your return fax number.

Leave the line blank, or give a fax machine that can receive. Without a return fax number, the IRS’s manual says the confirmation letter (notice CP 575) is mailed to the address on lines 4a and 4b and takes about two weeks to arrive.

Write lines 4a and 4b clearly. The IRS manual says that when that mailing address can’t be read and there’s no return fax number, the application is treated as waste, with no EIN and no reply. If anything else is missing, the IRS writes to that address to ask for it.

The IRS’s processing-status page, updated on 16 October 2026, put faxed SS-4s at about eight business days after receipt, longer than the four days on the EIN page. Mailed applications take up to 30 days to process, and the instructions say a mailed application gets its EIN in about four weeks.

Entries that hold up an SS-4

• One EIN a day. A responsible party can get only one EIN per business day, by any method.
• One method per entity. The IRS asks you to apply only once, so the entity doesn’t end up with two EINs.
• Register first. A new LLC, partnership or corporation should be registered with its state before it applies.
• Line 4a and 4b must be the entity’s own mailing address, not a third party’s.
• Lines 7a and 7b: the responsible party must be a person, not a company, unless the applicant is a government entity.
• Line 9a: if your type of entity isn’t listed, tick “Other” and describe it. Don’t write “N/A”.
• Line 10: tick the reason you’re applying. Line 17 also needs an answer.
• Names and addresses: the IRS’s systems take only letters, numbers, hyphens and ampersands in a business name, and 35 characters for a street address.

Signatures and third-party designees

When a signature is needed, the instructions say who gives it: the individual applicant, the president, vice president or another principal officer of a corporation, a responsible and authorized member or officer of a partnership or other organization, or the fiduciary of a trust or an estate.

If someone else, such as an accountant, applies for you and should receive the EIN, fill in the third-party designee section and sign it by hand. The IRS manual says it doesn’t accept an electronic signature for this authorization, and must receive the form within 120 days of the date you signed. Without a valid signature, the IRS still assigns the EIN but doesn’t give it to the designee.

How to fax Form SS-4 with FaxTonic

1. Fill in Form SS-4 from irs.gov: it’s a fillable PDF that the IRS says is suitable for faxing. Leave the return fax line blank, and sign it if a signature applies to you.
2. Save the completed form as a PDF, or scan it if you signed on paper. FaxTonic takes PDF, JPEG, and PNG files, up to 4 MB once prepared for faxing.
3. Open FaxTonic and add your file. The cover page is free and optional; if you keep it, put “Form SS-4” in the subject and add a phone number.
4. Choose the United States, enter 855-641-6935 or the number for applicants outside the states, and check the price: $1.49 a page.
5. Pay by card and save a screenshot of the delivered status page. Then watch the mail at the address on lines 4a and 4b. The IRS’s manual says that after the fourth business day, the applicant can call the IRS to have the EIN confirmed by phone.