EIN, ITIN or SSN: the US tax IDs a non-resident actually needs

If you are a non-resident forming or running a US company, you have probably encountered three acronyms that look deceptively similar: EIN, ITIN and SSN. Each serves a different purpose, applies to different people, and is obtained through a different process. Getting them mixed up is one of the most common and most expensive mistakes foreign founders make. Some spend months chasing a number they will never use, while others skip a filing they genuinely need. This guide, current as of 2026, breaks down the differences between EIN, SSN and ITIN so you can identify exactly which US tax IDs apply to your situation, apply in the right order, and avoid wasted time. Note that IRS processes change periodically: always confirm current requirements before filing.

Three numbers, constantly confused

The US tax system assigns identification numbers to both people and entities. The confusion arises because all three numbers share a similar nine-digit format, yet they exist for fundamentally different reasons. An SSN identifies a person authorised to work in the US. An EIN identifies a business entity. An ITIN identifies a foreign individual who has a US tax filing obligation but cannot get an SSN.

Non-residents routinely conflate these three. A typical error: believing you need an SSN or ITIN before you can obtain an EIN for your LLC. You do not. Another common mistake: applying for an ITIN "just in case" when you have no personal US filing obligation. That application will be rejected, and you will have delayed your actual priorities by weeks or months.

The practical rule is simple. You almost always need an EIN for the company. You need an ITIN only if you personally must file a US tax return. And unless you have US work authorisation, the SSN is irrelevant to you entirely.

SSN: what it is, and why a non-resident usually cannot get one

A Social Security Number is issued by the Social Security Administration to US citizens, permanent residents and individuals with valid US work authorisation. It was originally designed to track earnings for Social Security benefits, but it has become the default personal identifier across American financial and tax systems.

If you are a non-resident business owner living outside the US, you almost certainly do not qualify for an SSN. You would need a visa category that permits employment in the United States, such as an H-1B or L-1, along with a physical presence to apply in person at a Social Security office. Simply owning a US LLC or C-Corp does not grant work authorisation and therefore does not entitle you to an SSN.

This is good news, not a problem. You do not need an SSN to form a company, obtain an EIN, open most business bank accounts, or file your entity's tax returns.

EIN: your company's number, no SSN required

An Employer Identification Number is the tax identifier for your business entity: your LLC, C-Corp, partnership, or any other structure registered in the US. Think of it as the company's equivalent of a personal tax number. You need it to file business tax returns, open a US business bank account, hire employees, and comply with IRS reporting requirements.

The IRS issues EINs through Form SS-4. US-based applicants with an SSN can apply online and receive their number instantly. International applicants without an SSN or ITIN have three routes: fax the completed SS-4 to the IRS (typical turnaround of four to six weeks), post it, or call the IRS international phone line during business hours. On the form, the foreign responsible party simply enters "Foreign" in the SSN/ITIN field.

A critical point that many non-residents miss: an EIN is not an SSN, and obtaining one does not require an SSN or ITIN. The two are independent. Your company can have an EIN while you, the owner, hold no US personal identification number at all. Having an EIN also does not, by itself, create a US tax liability for you personally.

ITIN: your personal number, only when you must file

An Individual Taxpayer Identification Number is a personal tax-processing number issued by the IRS to individuals who have a US tax filing obligation but are not eligible for an SSN. You obtain it by submitting Form W-7, typically alongside the tax return that creates the filing requirement.

The key word is "obligation." You need an ITIN only if you must file a personal US tax return, such as Form 1040-NR, because you have effectively connected income in the US, or if you are claiming treaty benefits, or if withholding agents require it. Merely owning an LLC does not automatically trigger a personal filing obligation, and therefore does not automatically require an ITIN.

This is where many non-residents waste significant time. They assume they need an ITIN to get an EIN, or that LLC ownership alone demands one. Neither is true. If your single-member LLC has no effectively connected income and you have no other US filing requirement, an ITIN application will likely be rejected because you cannot attach the required tax return to justify it.

Which one you actually need, and when

For most non-resident founders, the decision tree is straightforward:

• You are forming a US LLC or corporation: you need an EIN. Full stop.
• You have effectively connected income, need to claim treaty benefits, or have another personal US filing obligation: you need an ITIN in addition to the company's EIN.
• You have US work authorisation and are physically present: you may qualify for an SSN, which then serves as your personal identifier in place of an ITIN.

A foreign-owned single-member LLC still must file Form 5472 with a pro-forma Form 1120 each year, reporting transactions between the LLC and its foreign owner. This filing uses the company's EIN, not a personal number. Many founders confuse this entity-level obligation with a personal tax return, but they are separate things.

If you are unsure whether you have a personal filing obligation, that is a question for a US-licensed tax adviser, not something to guess at. The cost of professional advice here is far lower than the cost of applying for the wrong number, missing a deadline, or triggering unnecessary IRS correspondence.

How to apply for each as a non-resident

EIN (Form SS-4)

Prepare the completed form with your company's legal name, entity type, formation state and date, and the responsible party's foreign address. Enter "Foreign" where the form asks for the responsible party's SSN or ITIN. Submit by fax or post to the IRS, or call their international line at +1 267-941-1099 (Monday to Friday, 6 a.m. to 11 p.m. Eastern Time). Fax applications typically return a number within four to six weeks. Phone applications can yield a number during the call itself, though hold times vary.

ITIN (Form W-7)

Complete Form W-7 and attach it to the federal tax return that creates your filing requirement. You must also include original identity documents (passport) or certified copies from the issuing agency. The IRS does not accept notarised photocopies. Alternatively, you can use an IRS-authorised Certifying Acceptance Agent, who can verify your documents so you do not need to post your original passport. Processing typically takes seven to eleven weeks.

SSN

Apply in person at a US Social Security Administration office with your passport, visa, and I-94 arrival record. This is only relevant if you hold valid US work authorisation.

Cosmos coordinates US company formation and EIN applications through licensed US partners, handling the paperwork and IRS communication so you do not need to manage international fax timelines or phone queues yourself.

Common mistakes and delays

Applying for an ITIN without a valid tax return is the single most frequent error. The IRS will reject the W-7, and you will have sent your original passport overseas for nothing. Always confirm you have a genuine filing obligation before starting the ITIN process.

Other pitfalls that cause weeks of delay:

• Entering incorrect entity information on Form SS-4, especially mismatches between the company name on file with the state and the name on the form
• Using a PO Box as the responsible party's address when the IRS expects a physical street address
• Submitting notarised passport copies for an ITIN application instead of certified copies or using a Certifying Acceptance Agent
• Assuming an EIN alone satisfies all reporting requirements, while forgetting the annual Form 5472 obligation for foreign-owned single-member LLCs

Each of these mistakes resets the clock by weeks. If you are working with banking deadlines, contract signings, or investor timelines, that delay can be genuinely costly.

How Cosmos helps

Cosmos works with licensed US partners to handle the formation-to-EIN pipeline for non-resident founders. That means your company registration, registered agent setup, and EIN application move through a single coordinated process rather than three separate bureaucratic tracks. Where clients have a genuine ITIN requirement, Cosmos can connect them with authorised tax professionals who manage the W-7 filing and document certification.

The value is not just speed: it is accuracy. A correctly completed SS-4 submitted through the right channel avoids the rejection-and-resubmission cycle that costs most DIY applicants an extra month or more. For founders who need to open a US bank account or sign contracts quickly, that time difference matters.

Frequently asked questions

Do I need an ITIN to form an LLC?

No. You can form an LLC and obtain an EIN without an ITIN or SSN. The ITIN is only necessary if you have a personal US tax filing obligation.

Can I use my EIN instead of an SSN for personal purposes?

No. An EIN identifies your business entity. It cannot be used on personal tax returns, for personal credit applications, or as a substitute for an SSN or ITIN in contexts that require a personal identifier.

Will getting an EIN make me liable for US taxes?

An EIN is an identifier, not a tax trigger. Your US tax liability depends on the nature of your income, your entity structure, and applicable tax treaties, not on whether you hold an EIN.

How long does it take to get an EIN as a non-resident?

By fax, expect four to six weeks. By phone, you may receive the number during the call. Processing times fluctuate, so confirm current IRS timelines before planning around a specific date.

What is Form 5472, and does it affect which ID I need?

Form 5472 is an information return that foreign-owned single-member LLCs must file annually with a pro-forma Form 1120. It uses the company's EIN. It does not require you to have an ITIN unless you also have a separate personal filing obligation.

The distinction between EIN, ITIN and SSN is not complicated once you see each number for what it is: a company identifier, a personal tax-processing number for non-residents, and a work-authorised personal identifier, respectively. Most non-resident founders need only an EIN. If your situation requires an ITIN, get professional guidance to ensure your W-7 is filed correctly the first time. If you are ready to form your US company and secure your EIN without the guesswork, Cosmos can help you get it done properly from the start.

This is general information, not tax, legal or accounting advice. Rules differ by country and change frequently; confirm your position with a qualified adviser in the relevant jurisdiction before acting.