Form SS-4 is the application that gets your US company an EIN — the federal tax ID every US LLC and C-Corp needs. It's a single page. Most fields are straightforward. The one that consistently confuses non-resident founders is line 7b: "Phone number of responsible party" (and the company phone line on the form's signature block).
What goes there? Will the IRS actually call? What if you don't have a US phone yet? This article covers it.
What Form SS-4 Asks For
Form SS-4 has two phone-related lines:
- Line 7b — Phone number of responsible party: required, expects a phone where the IRS can reach the person responsible for the entity.
- Signature block, "Telephone number": required, the phone for the entity itself or the person signing the form.
In practice these can be the same number — your US business phone — for the simplest case. We'll cover the common variations below.
Will the IRS Actually Call?
Almost never. The IRS processes the SS-4 by mail, fax, or (for US residents) online. The phone number on the form is for follow-up if something on the application is unclear, not for routine notification.
Specifically, the IRS will call:
- If they need clarification on the responsible party's identity
- If documentation submitted with the form is illegible or missing
- For the rare audit-related follow-up that traces back years later
What this means in practice: the phone needs to be reachable — a real US number that goes to a real inbox, voicemail, or SMS — but it does not need to be a phone you sit by waiting for the IRS to dial.
What Counts as a Valid Phone for SS-4
The IRS does not publish a list of acceptable phone-number types for Form SS-4. They do, however, require that you provide a number where you can be reached.
In practice, the following all work:
- A US mobile carrier number (T-Mobile, Verizon, AT&T, US Mobile, Mint Mobile, etc.)
- A US virtual phone number from a licensed VoIP provider that routes voice and/or SMS
- A US landline (if you happen to have one)
- A non-US number with country code, in the rare case the form is filed without any US phone
For non-resident founders, the practical question is: should I put a US number or my home-country number?
US Number vs. Home-Country Number
Use a US number if you have one (or are about to get one — see below). Reasons:
- It signals "this entity is a real US business with real US contact info" rather than "this entity is a foreign founder filing paperwork from abroad". Both are legitimate; the first reads as lower friction to the IRS examiner reading the form.
- The same US number will be on your bank application, your Stripe profile, your W-9, and your business directory listings — keeping it consistent across forms reduces follow-up questions.
- If the IRS does send mail or follow-up, a US number is easier for IRS staff to dial.
Use your home-country number if you genuinely don't have a US number and don't plan to get one. The IRS will accept a properly-formatted international number with country code (e.g., +44 20 1234 5678). The application won't be rejected.
For almost all non-resident founders who are running a real US company — making sales to US customers, opening US bank accounts, listing the business publicly — the US number wins. The exception is the founder who is incorporating purely to hold IP or for some narrow tax-structure reason and will never publicly market the entity.
What If You Don't Have a US Phone Yet?
This is the most common situation: a non-resident is partway through Stripe Atlas / doola / Firstbase, the formation service has applied (or is about to apply) for the EIN, and they realize the SS-4 needs a phone.
Three options:
Option 1: Get a US virtual number before SS-4 is submitted
If you have a few days before SS-4 is filed, get a US virtual number. Acquisition takes minutes online. Then enter that number on the SS-4. Use the same number on every subsequent form (bank application, Stripe, W-9, etc.).
This is by far the most common path and the one we'd recommend. A virtual US number from a $7/month provider does what an SS-4 phone field needs.
Option 2: Use a temporary number that you'll replace
If you're truly in a rush and don't have time to set up a number before the SS-4 deadline, you can enter your home-country number on the SS-4. Then get a US number afterwards and use it on all subsequent forms. The SS-4 itself will keep your home-country number on file, but no one will ever look at it again.
Option 3: Let the formation service handle it
Stripe Atlas, in particular, files the SS-4 for you and uses some of their own contact info as part of the process. They will still ask you for a "responsible party phone" — that's where the above applies.
Common SS-4 Phone Mistakes
The following slow down or complicate EIN approval more than the IRS publicly admits:
Mistake 1: Listing the formation service's phone as yours
Some founders, anxious about putting their own number on a federal form, enter the phone number of their formation service or registered agent. Don't do this. The IRS expects the responsible party's reachable number, not a third party's. If the IRS calls the registered agent looking for you, the registered agent (correctly) won't know who you are.
Mistake 2: Using a number that requires extension-routing
If you put "+1 800 555 0100 ext 1234" with extension routing, the IRS staff who calls will hear "press 1 for sales, press 2 for support". They won't navigate the IVR. Use a direct number that rings to you (or your voicemail / SMS forwarding).
Mistake 3: Inconsistency with later forms
If your SS-4 lists phone A, your bank application lists phone B, and your W-9 lists phone C, you're creating verification friction at every step. Use one US phone everywhere.
Mistake 4: Phone disconnected after EIN is approved
Some non-residents get a temporary US phone for the SS-4 application, then let it expire. Two years later, the IRS sends a routine notice, can't reach the responsible party, and the company has a (very minor) compliance hassle. Keep the same US phone for the life of the entity if you can.
A US phone number that won't disappear
IncNumber is $7/month. The same number stays with your US LLC for years. SMS forwarded to email. Built for non-US founders.
Get your US number →What About the Responsible Party Name?
While we're at it: the SS-4 also asks for the "responsible party" name (line 7a). For a single-owner non-resident LLC, this is you, not your formation service, not your registered agent. The IRS specifically wants the actual person who controls the entity.
The IRS clarified in 2017 that the responsible party must be a natural person (not another entity) and must be someone with actual control over the entity. Non-residents are explicitly allowed to be the responsible party; you do not need a US co-founder or US-resident responsible party to apply.
Filing Methods for Non-Residents
For US residents, the IRS offers an online EIN application. For non-residents without an ITIN or SSN, you must apply by fax or mail using the SS-4 form.
- Fax: The fastest non-online method. The IRS international fax number is +1 855-641-6935. EINs are typically issued in 4-6 weeks but can be faster.
- Mail: Slower, often 8-12 weeks.
- Online via formation service: Many founders let Stripe Atlas, doola, or Firstbase handle this. They essentially fax SS-4 on your behalf with your info pre-filled.
If you fax SS-4 yourself, you'll need an outgoing fax service. The cheapest path is a per-use online fax — typically $1.50-$3 to send a single SS-4 to the IRS, no subscription needed.
Bottom Line
The phone on SS-4 should be a real US phone you control, reachable by voicemail or SMS, that you'll keep using on every subsequent form for the life of your US company. If you don't have a US phone yet, get one before submitting SS-4. The $7-$19/month options that exist all work for this — the SS-4 phone field doesn't run VoIP-detection or carrier classification.
The IRS will almost certainly never call. But on the rare occasion they do, you'd rather have a number that goes to your inbox than a disconnected line two years later.