How to Fax IRS Form SS-4 Online (EIN Application) | SecurelyFax

Form SS-4 is the IRS application for an Employer Identification Number. Fax is one of the methods the IRS lists in the SS-4 instructions, and when you include a return fax number on the form, the IRS generally faxes the EIN back within about four business days. SecurelyFax sends your completed SS-4 from email, a browser upload, or a phone scan — no fax machine and no phone line.

What Form SS-4 does

Form SS-4 is how a new business, estate, trust, non-profit, or other entity applies for an EIN — the federal tax identification number used to open business bank accounts, file payroll, and hand to vendors that need a W-9. The form itself is short, but it has to be completed correctly because the EIN it generates follows your entity from then on.

Why people choose fax over mail for SS-4

Mail can take weeks. Fax with a return fax number is the fastest paper path: the IRS generally faxes the EIN back within about four business days, which is critical when a bank, payroll provider, or contract is waiting on the number. The online EIN application is faster still when your situation supports it, but fax is the standard fallback when the online path is not available.

How to fax Form SS-4 through SecurelyFax

1

Complete and sign Form SS-4

Fill out every required field. The responsible-party signature line is required.
2

Enter your return fax number on the form

This is the key step. Without it, the IRS will mail the EIN instead of faxing it back, which is much slower.
3

Look up the current destination fax number

Use the destination number listed on the latest official Form SS-4 instructions for your state. It can change; do not rely on numbers from old guides.
4

Send through SecurelyFax

Email, browser upload, or phone scan all work. Pick the option that matches where the signed form already lives.
5

Save the delivery confirmation

Keep the SecurelyFax send receipt with your business formation records.

Where to find the current SS-4 fax number

The IRS prints the destination fax number on the Form SS-4 instructions PDF, not on the form itself. The number depends on the location of your business or the responsible party. Always pull the latest instructions from IRS.gov so you are using the current number for your situation.

SecurelyFax is not affiliated with the IRS, is not a tax authority, and cannot file Form SS-4 on your behalf. It transmits your completed, signed form to the destination number you provide and returns a delivery confirmation. The IRS instructions are the source of truth for what method and number to use.

Frequently asked questions

Can I fax Form SS-4 to the IRS?

Yes. The IRS lists fax as an accepted submission method for SS-4 in the form's current instructions.

How long does the EIN take to come back by fax?

When you include a return fax number on the form, the IRS generally faxes the EIN back within about four business days.

What happens if I forget the return fax number?

The IRS will mail the EIN to the address on the form instead of faxing it back, which can take weeks. Adding the return fax number is the key step that triggers the faster fax response.

Which SS-4 fax number should I use?

Use the destination number printed on the latest Form SS-4 instructions for your state. SecurelyFax cannot assign or override IRS numbers.

Do I need a fax machine to send SS-4?

No. You can email, upload, or scan with your phone — SecurelyFax handles the transmission.

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Last reviewed: 2026-05-30