Application for employer identification number form ss-4: Co

If you're a UK founder setting up a business in the United States, your first major piece of admin is getting an Employer Identification Number (EIN). This is done by filing Form SS-4, the Application for Employer Identification Number, with the IRS.

Think of an EIN as a national insurance number, but for your company. It’s a unique nine-digit code that officially registers your business with the U.S. tax authorities, and you'll need it for just about everything.

Why Your US Business Needs an EIN

An Employer Identification Number is how the Internal Revenue Service (IRS) identifies your business for tax purposes. For any founder based outside the US, getting an EIN isn't just a good idea—it's an absolute necessity for your business to operate legally and financially. Without one, you’re essentially at a standstill.

This nine-digit number, always formatted as 12-3456789, is assigned to US business entities like corporations and LLCs. In the past, the only options were to mail or fax in your Form SS-4, which could mean a long wait. While the IRS now has an online system, it’s really only for applicants with a US social security number, so international founders still rely on the traditional methods. And you’re not alone—the IRS issues over 5.5 million EINs annually, a testament to how crucial this number is. For the official details, you can always check the IRS website's page on Form SS-4.

Key Reasons an EIN Is Non-Negotiable

As a UK entrepreneur, you'll quickly find that many fundamental business activities in the US are impossible without an EIN.

• Opening a U.S. Business Bank Account: This is the big one. Virtually all US banks will ask for your company's EIN to open a business account. It's essential for keeping your personal and business finances separate, which is critical for liability protection.

• Hiring U.S. Employees: If you plan to build a team in the States, you must have an EIN to manage payroll and handle employment taxes correctly.

• Filing Federal Tax Returns: Your EIN is required on all federal tax forms, from annual income tax returns to employment tax filings.

• Building Business Credit: An EIN is the first step in establishing a credit profile for your business, completely separate from your personal credit history back home.

I always tell founders: your EIN is the key that unlocks the US banking and tax system. It’s the piece of paper that proves your business is real in the eyes of the IRS, banks, and suppliers. It turns your US venture from an idea into an actual, operational company.

Who Must File an Application for Employer Identification Number Form SS-4

Don't let the name fool you. An "Employer" Identification Number isn't just for businesses with employees. The IRS requires a wide range of business structures to have an EIN, whether they have a payroll or not.

If you’ve set up your US business as one of the following, you must get an EIN:

• Corporation (either a C Corp or S Corp)

• Partnership

• Multi-member Limited Liability Company (LLC)

Now, here’s a common point of confusion for solo founders. Technically, a single-member LLC with no employees doesn't need an EIN for tax filing. However, in practice, you absolutely will. Try opening a US bank account for your single-member LLC without one—it’s not going to happen.

My advice is always the same: even if you’re a sole proprietor or a single-member LLC, just file the Form SS-4 and get your EIN. It’s a straightforward step that saves you from major roadblocks later on.

A Line-by-Line Guide to Completing Form SS-4

At first glance, a US government document like the application for employer identification number form ss-4 can look pretty daunting. But don't worry—it's more of an introduction for your new company than an exam. For UK founders, a couple of lines can be tricky, but I'll walk you through how to fill it out correctly so you can get it right the first time.

Let's break down the key fields, paying close attention to the spots that tend to trip up non-resident entrepreneurs.

Lines 1-2: Legal Name and Trade Name

Line 1 (Legal name of entity): This is the most important field on the entire form. The name you enter here must exactly match the legal name on your company’s formation documents, like your Articles of Incorporation. If your company is registered as "Innovate UK Tech Inc.", you need to write exactly that—not "Innovate UK Tech." Any little difference will get your application kicked back.

Line 2 (Trade name of business): This is for your "Doing Business As" (DBA) name. For example, if "Innovate UK Tech Inc." does business under the brand "InnovateNow," you'd put "InnovateNow" here. If you don't have a separate trade name, just leave this line blank. Simple.

Lines 4a-4b: Mailing and Physical Addresses

Line 4a (Mailing address): This is where the IRS will send all official mail, including your EIN confirmation letter (if you apply by post). Your UK address is perfectly fine here, but you could also use a US-based virtual address. Just make sure it's accurate.

Line 4b (Street address): If your business physically operates from a different address than where you get mail, enter it here. For most UK founders running remote-first companies, this will likely be the same as the mailing address, so you can either re-enter it or leave it blank.

Pro Tip: Using a US-based virtual address or your Registered Agent's address for both lines can really simplify things. It gives your business a clear US footprint from the get-go, which definitely helps when you start opening bank accounts and dealing with other admin.

Lines 7a-7b: The Responsible Party

This is, without a doubt, the section that causes the most headaches for international founders. The Responsible Party is the individual person who has ultimate control over the company. It's never the company itself.

• Line 7a (Name of responsible party): Enter the full name of the main founder or director. For a new UK-founded startup, that’s almost certainly you.

• Line 7b (SSN, ITIN, or EIN): Since you're a UK founder and likely don't have a US Social Security Number (SSN) or Individual Taxpayer Identification Number (ITIN), just write "Foreign" in this box. Critically, do not leave it blank. Writing "Foreign" is the correct protocol and signals to the IRS that you're a non-resident applicant.

Nailing down the Responsible Party is non-negotiable. You can learn more about defining the Responsible Party to make sure you've got the right person listed.

Lines 9a and 10: Entity Type and Reason for Applying

Line 9a (Type of entity): Here, you'll tell the IRS about your business structure. Check the box that matches how you registered your US company.

• Corporation: This is what you’ll check for a C Corp.

• Other (specify): This is the one for a Limited Liability Company (LLC). You need to check the box and then write in "Limited Liability Company," "Single-Member LLC," or "Multi-Member LLC," depending on your setup.

As you can see, getting an EIN isn't just a bit of paperwork—it's fundamental to operating in the US.

Without it, you can't open a business bank account, hire employees, or file your taxes. It's truly the key that unlocks your ability to grow.

Line 10 (Reason for applying): For most brand-new companies, you'll check the box for "Started a new business (specify type)." Then, on the line provided, write your business type again (e.g., "C-Corporation" or "LLC"). This is almost always the right choice for a new venture.

Lines 11-13: Key Dates and Employee Counts

Line 11 (Date business started or acquired): Don't overthink this one. This is simply the official formation date of your company—you can find it on the registration certificate from the state (like Delaware or Wyoming).

Line 12 (Closing month of accounting year): For virtually all new C Corps and LLCs, the answer here is December. The US tax year is aligned with the calendar year, so stick with that unless you have a very specific reason not to.

Line 13 (Highest number of employees expected in the next 12 months): Just give your best, most reasonable estimate. If you plan on hiring a small team of five US-based employees, enter "5." If you have no immediate hiring plans, just enter "0" for both non-agricultural and agricultural. You can ignore the "household" box.

Lines 16-17: Describing Your Business Activity

These last two fields are where you give the IRS a clear, quick snapshot of what your business actually does. Be specific, but keep it brief.

Line 16 (Check one box that best describes the principal activity): Pick the category that's the closest fit.

• Retail

• Wholesale

• Other (specify): Many tech startups, consultancies, and digital service businesses will fall into this category. If you check "Other," you'll need to provide a short description, like "SaaS provider for marketing analytics" or "E-commerce brand consulting."

Line 17 (Principal products or services): Get a little more specific here. The IRS agent reviewing this needs to understand what you do at a glance.

• Good example: "Selling sustainable pet supplies via an online store."

• Bad example: "Business."

The more clearly you can describe your business, the less likely you are to face delays. By taking the time to fill out each line of the application for employer identification number form ss-4 with care, you set yourself up for a smooth and quick approval.

Alright, you’ve filled out your Form SS-4. Now for the crucial part: getting it to the IRS.

While US-based founders get to use a simple online portal, that door is closed for international applicants who don't have a US tax ID number. For UK founders, this means you’re left with a few old-school, but reliable, methods. The one you choose will have a huge impact on how quickly you can get your business up and running.

Submitting by Fax: The Go-To Method

When I’m advising founders, I almost always recommend faxing the application for employer identification number form ss-4. It’s, without a doubt, the fastest and most efficient way for anyone outside the US to get their EIN.

The IRS runs a dedicated fax line just for international applications, so your form lands on the right desk instead of getting lost in the domestic pile.

International Fax Number:

The turnaround is impressive. You can usually expect to have your new EIN faxed back to you within 4-7 business days. Compared to the snail's pace of mail, this is a game-changer.

To make sure everything goes off without a hitch, I always tell clients to include a simple cover sheet. Just a quick note with this info:

• Your company name

• Your name (as the contact person)

• Your return fax number—this is absolutely critical!

• Your phone number and email

It’s a tiny extra step, but it helps the IRS agent get the confirmation right back to you without any guesswork.

Submitting by Mail: The Slow Road

If you absolutely can't get to a fax machine or use an online fax service, you can mail your Form SS-4. But I have to be blunt: be ready for a long, long wait. Processing a mailed application can take anywhere from four weeks to two months, and if the IRS is experiencing backlogs, it can be even longer.

This kind of delay can bring your US launch to a screeching halt, blocking you from opening a bank account or getting payroll set up. If you have no other choice, send your signed form to this specific address:

Internal Revenue Service Attn: EIN International Operation Cincinnati, OH 45999 USA

Honestly, mailing should be your last resort. It’s well worth a few pounds for an online fax service to avoid weeks of anxious waiting.

Applying by Telephone: The Wildcard Option

There's a third, less-travelled path: applying over the phone. The IRS has a business tax line specifically for international founders.

• IRS International Applicant Phone Line: (This is a US number, so international charges will apply.)

Their team is available from 6:00 a.m. to 11:00 p.m. Eastern Time, Monday to Friday. Before you call, make sure you have the completed Form SS-4 right in front of you. The agent will walk you through the form line by line, and if everything is in order, they can issue your EIN right there on the call.

The biggest hurdle here is the notoriously long hold times. It’s a trade-off: you could spend an hour on hold but get your EIN instantly, or you could send a fax and wait a few days.

No matter which method you choose, the IRS will eventually mail you an official EIN confirmation, Letter CP 575. This document will be sent to the company address on your form, and it can take several weeks to arrive in the UK. If you need official proof of your EIN sooner, you can request a specific verification letter. You can read our guide on obtaining an EIN verification letter to learn how that works.

Common Mistakes to Avoid on Your EIN Application

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Getting your application for employer identification number form ss-4 submitted is a fantastic feeling, but even a tiny mistake can bring the whole process to a dead stop. The IRS system is incredibly precise. As an international founder applying by fax, getting it right the first time is non-negotiable if you want to avoid delays that can stretch on for weeks.

Think of this as your final pre-flight check before sending that fax. I’ve seen hundreds of these applications, and these are the most common slip-ups UK founders make and how you can sidestep them.

Mismatched Legal Name and Formation Documents

This is, without a doubt, the number one reason for rejection. The legal name you put on Line 1 of your Form SS-4 must be an exact mirror of what’s on your company's official formation documents, like your Certificate of Incorporation.

For example, if your company is officially registered as "London FinTech Solutions, Inc.", you can't just write "London FinTech Solutions" or "London FinTech Inc." Even a missing comma or an extra space can get your application kicked out by the system.

Before you even think about faxing it, lay your formation document and your completed Form SS-4 side-by-side. Compare Line 1 character-for-character. Seriously. This five-second check can save you weeks of frustration.

Incorrect or Incomplete Responsible Party Details

The IRS needs to know which human being has ultimate control over your company. They call this person the "Responsible Party," and botching this section is another surefire way to get your application denied.

Here are the most common pitfalls I see:

• Leaving Line 7b Blank: This is a huge red flag. As a non-resident without a US tax ID, you should never leave this box empty. You must write "Foreign". This instantly tells the IRS agent why there's no SSN or ITIN.

• Listing a Company: The Responsible Party has to be an individual person. It can never be another business.

• Vague Name: Use the full, legal name of the director or founder. No nicknames, no abbreviations.

A correctly filled-out Responsible Party section is like a green light for the IRS agent reviewing your file. It shows you understand the specific rules for international applicants and have given them exactly what they need, which can seriously speed things up.

Choosing the Wrong Entity Type or Reason for Applying

Lines 9a and 10 tell the IRS what kind of business you are and why you need an EIN. Any confusion here just creates problems.

For instance, a lot of UK founders form an LLC in the US. When you get to Line 9a, you have to check the "Other (specify)" box and then write in "Limited Liability Company". Just checking the box is not enough.

For Line 10, "Reason for applying," nearly every new UK-founded US business should be selecting "Started a new business." Don't overthink it. The IRS is built for volume and precision, and selecting a less common option can sometimes trigger extra scrutiny. For international filers, accuracy on the faxed form is everything, as an invalid reason can lead to an automatic rejection. You can find more details about these IRS form specifics to make sure every box is ticked correctly.

What to Do If Your Application Is Delayed or Rejected

Faxed your application and haven't heard anything back in 7-10 business days? It’s likely there was an issue. Don't panic. The most common cause is a simple mistake on the form.

The IRS generally won't call you to fix minor errors on an application sent by fax. They just... won't process it. If you suspect a delay, here’s your best move:

1. Review Your Original Form: Pull out the copy of the Form SS-4 you sent and scrutinize it. Check it against the common mistakes I mentioned above.

2. Correct and Resubmit: Found a potential error? Grab a fresh copy of the form and fill it out correctly.

3. Fax Again: Send the corrected application for employer identification number form ss-4 with a brand new cover sheet.

Being proactive like this is far better than waiting around for a rejection notice that might never even show up. By double-checking your work before you submit, you can turn a potential showstopper into a minor speed bump.

Got Your EIN? Here’s What to Do Next

Congratulations—that nine-digit Employer Identification Number has landed. After navigating the application for employer identification number form ss-4 and sending it off, getting your EIN is a huge step forward. It’s the official nod from the US government that your business is on the map.

But getting the EIN is like getting the keys to a new car; it doesn’t mean you’ve arrived at your destination. Now it's time to actually start the engine. A few immediate and crucial tasks are waiting to get your company fully operational and ready to do business in the States.

First Things First: Protect Your EIN Letter

Whether you got your number over the phone or waited for the post, the IRS will send an official confirmation notice. This document, the Letter CP 575, is the definitive proof of your EIN. It's a foundational document for your company, and you’ll need it for just about everything.

I can't stress this enough: guard this letter carefully.

• Store the Original Securely: File the original CP 575 away with your company formation documents.

• Make Digital Backups: Scan a high-quality copy and save it in at least two places, like a secure cloud drive and a local hard drive.

A quick heads-up: if you lose your CP 575, the IRS won't issue a direct replacement. You can request a 147C Letter, which serves the same purpose as official verification, but it's an extra step you can easily avoid by protecting the original from day one.

The Big One: Opening Your US Business Bank Account

This is almost certainly your most urgent next step and the main reason you rushed to get an EIN in the first place. A dedicated US business bank account is non-negotiable. It keeps your business and personal finances separate, which is vital for protecting the limited liability status of your LLC or corporation.

It also makes bookkeeping and tax season worlds easier. US banks will always ask for your EIN and formation documents to open a business account. With your CP 575 in hand, you're all set. Before you start, it’s a good idea to review the documents required to open a U.S. company bank account to make sure you have all your ducks in a row.

Get Ready for Ongoing US Compliance

Your EIN isn't just for setup; it’s a permanent part of your business's identity for its entire life. This includes all your ongoing tax and reporting duties at both the federal and state levels.

You’ll be using your new EIN for all sorts of things, including:

• Filing Federal and State Taxes: Every business tax return you file will require your EIN.

• Running Payroll: If you hire US-based employees, you'll need the EIN to register for payroll taxes and manage all the necessary withholdings.

• Registering for Sales Tax: If you have a significant business presence—known as "nexus"—in certain states, you’ll use your EIN to register for and remit sales tax.

Keep the IRS in the Loop: Reporting Business Changes

As your company grows and evolves, you’ll need to let the IRS know about any major changes. It's a simple step that's easy to forget but can cause compliance headaches later. The official way to do this is with Form 8822-B, Change of Address or Responsible Party.

You are required to file this form if you:

• Change your business's mailing address.

• Move your business to a new physical location.

• Appoint a new "Responsible Party"—the person named on your original Form SS-4.

Keeping this information up-to-date ensures you never miss important notices from the IRS and stay in their good books. Your EIN is permanent, but the details attached to it need to stay current. Once these items are ticked off, your business is truly ready for action.

Common Questions from UK Founders

Even after a line-by-line walkthrough, a few key questions always pop up. Let's tackle the most common ones we hear from UK founders to clear up any final confusion about the Form SS-4.

What if I Don’t Have a U.S. Social Security Number?

No problem at all. In fact, this is the standard situation for most international founders, and the IRS has a clear process for it. You won't be able to use the quick online portal, as that's reserved for applicants with an existing U.S. tax ID.

Instead, you'll apply by fax or mail. When you get to the line on Form SS-4 asking for the Responsible Party's SSN or ITIN, you simply write “Foreign.” That’s the official signal to the IRS that you’re a non-resident applicant, and it ensures your form is routed and processed correctly.

How Quickly Will I Get My EIN by Fax?

Sending your application by fax is by far the quickest method if you're outside the U.S. While official timelines can shift, we typically see the IRS send back the EIN within 4 to 7 business days.

This is a world away from applying by mail, which can stretch on for two months or more. A quick pro tip: make sure your completed form is clean and legible, and always include a basic cover sheet with your return fax number clearly visible. This small step helps the agent send your new EIN back without any hitches.

Who Exactly Is the "Responsible Party"?

Think of the Responsible Party as the one individual the IRS can hold accountable for the company. This person has ultimate control over the business and its finances. Getting this right on Lines 7a-7b is absolutely critical—mistakes here are one of the top reasons for an application to be rejected.

For a new UK-led company, this will almost always be the primary founder, director, or owner. It must be an individual person, never another company. The good news is that the Responsible Party does not need to be a U.S. citizen or resident, so it's a straightforward decision for most international founders.

Key Takeaway: The IRS needs to trace control of the company back to a real human being. Naming the correct individual as the Responsible Party is a non-negotiable step for a smooth application.

Do I Need a New EIN for a Name Change?

This one trips a lot of people up. If you're only changing your business's legal name but the underlying structure remains the same, you do not need a new EIN. You’ll simply notify the IRS of the name change when you file your next tax return.

However, if you change your company's core legal structure, you absolutely will need a new EIN. A classic example is moving from a sole proprietorship to an LLC or a corporation. That change creates a brand-new legal entity in the eyes of the IRS, which means you need to get a new Employer Identification Number for it.

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Getting your U.S. company set up from the UK has its hurdles, but you don't have to figure it all out on your own. At Set Up Stateside, we live and breathe this stuff, helping UK founders form, manage, and grow their U.S. businesses every day. From the EIN application to ongoing tax compliance, we're here to be your dedicated partner. Learn more about how Set Up Stateside can help.