Form SS-4 is filled in, signed and ready to go — everything below is about getting it to the right IRS unit. Filling the form in is a separate task, and the online application is out of scope here: that channel is open only to applicants whose responsible party holds an SSN or ITIN, as how to get an EIN without an SSN or ITIN explains.
Which fax number should I use for Form SS-4?
The Instructions for Form SS-4 split applicants by one test with three parts: does the entity have a legal residence, principal place of business, or principal office or agency in one of the 50 states or the District of Columbia? Entities that do use one number; the rest use one of two, depending on where the fax is sent from. 1,2
| Your situation | Fax number | Sending from |
|---|---|---|
| Legal residence, principal place of business, or principal office or agency in one of the 50 states or D.C. | 855-641-6935 | — |
| None of those in the 50 states or D.C. | 855-215-1627 | Inside the United States |
| None of those in the 50 states or D.C. | 304-707-9471 | Outside the United States |
Numbers verified against the IRS instructions as of August 2026. A foreign-owned company can still belong in the first row. A Delaware LLC owned from abroad but operating out of an office in Miami has its principal place of business in Florida, so it uses the domestic number. 1
Where do I mail Form SS-4 instead?
Mail goes to the same two units, split by the same three-part test. Use it when your fax cannot receive a reply, or when you have no fax at all. Both addresses come from the Instructions for Form SS-4, checked in August 2026. 4,5
| Your situation | Mail to |
|---|---|
| Legal residence, principal place of business, or principal office or agency in one of the 50 states or D.C. | Internal Revenue Service, Attn: EIN Operation, Cincinnati, OH 45999 |
| None of those in the 50 states or D.C. | Internal Revenue Service, Attn: EIN International Operation, Cincinnati, OH 45999 |
What do I need before I send it?
Three things, and the instructions name each one. The fax number matters most: it is the only channel the IRS has for answering a fax.
- Provide your fax number. The instructions put it plainly: give the number so the IRS can fax the EIN back to you.
- Sign and date the application. For mailed applications the instructions state this as a step of its own.
- Send it whenever suits you. The Fax-TIN service runs 24 hours a day, 7 days a week.
How long does each route take?
Turnaround depends on the channel, and the gap between the fastest and the slowest is about a month. The figures below are the expectations published by the IRS, checked in August 2026. 8,9,10
| Route | Typical turnaround |
|---|---|
| Fax with a return fax number | About four business days |
| About four weeks | |
| Phone (no U.S. or territory presence) | During the call |
What can go wrong, and how do I avoid it?
Three failures follow directly from the rules above, and the form itself warns you about none of them.
Using the wrong unit. Domestic and international applications go to two separate operations, and the choice depends on where the entity is based rather than on the applicant's passport.
Leaving line 7b blank. The instructions are explicit: when the responsible party has no SSN or ITIN and is ineligible to obtain one, write "foreign" or N/A — an entry is required. That case is covered in how to get an EIN without an SSN or ITIN. 12
Using more than one method. The instructions say to use only one method per entity, precisely so the entity does not receive more than one EIN — faxing and then mailing the same form, for example. Omitting the fax number causes a different problem, not this one: the IRS is then left without a channel to fax the number back. 13,3
What if nothing arrives?
Wait out the published window first: about four business days after a fax, about four weeks after mailing. For the mail route the instructions also say to complete the form at least 4 to 5 weeks before you will need the number, which is the same expectation seen from the other side. 8,9,14
After that window, call rather than resend. The instructions give 800-829-4933 to verify a number or ask about the status of a mailed application. Resending through another channel can produce a second EIN for the same entity. 15,13
If the application comes back rejected, or the entity type on line 9a is not obvious from your documents, that is the point to involve a qualified U.S. tax professional rather than guess.