EIN vs ITIN vs SSN: what is the difference?

The IRS uses the term taxpayer identification number (TIN) for any number it uses to administer the tax laws. A Social Security number is issued by the SSA, and all other TINs are issued by the IRS.^[1] The three most people meet compare like this:

The IRS describes the EIN as also known as a federal tax identification number, used to identify a business entity.^[1]

No. An ITIN identifies a person and an EIN identifies a business, and the IRS keeps them apart: the Form SS-4 instructions say an EIN is for use in connection with your business activities only, and not in place of your SSN or ITIN.^[3]

The two do meet on one form. When a company applies for an EIN, Form SS-4 asks for its responsible party: the individual who ultimately owns or controls the entity or exercises ultimate effective control over it. Line 7b takes that person's SSN or ITIN.^[3] So the EIN goes to the company, and the owner's personal number is recorded next to it.

Both are nine-digit numbers for individuals, and both work on a tax return. The difference is who can get one and what it covers.

• SSN. The SSA can assign one to a US citizen, or to a noncitizen lawfully admitted for permanent residence or under other authority permitting work in the US. A noncitizen without work authorization can be assigned one only for a valid nonwork reason, such as a federal or state benefit they are otherwise entitled to, and that card is marked as not valid for employment.^[4] The SSA keeps a record of the wages and self-employment income reported for each number.^[5] The application is Form SS-5, with evidence of identity, age, and US citizenship or lawful alien status, and the service is free.^[1]
• ITIN. The IRS issues it to certain nonresident and resident aliens, their spouses and dependents who cannot get an SSN.^[1] You need one if you have a federal tax purpose and are not eligible for an SSN. You have a federal tax purpose when you are legally required to file a US federal income tax return, want to file a return to claim a refund or tax benefit or report income, can be claimed as a spouse or dependent for an allowable tax benefit, or must provide a tax number for another federal tax purpose.^[2]

An ITIN is issued for federal tax purposes only. The IRS lists what it sits apart from: it does not qualify you for Social Security benefits or the Earned Income Tax Credit, provide or change immigration status, authorize work in the US, or serve as identification outside the federal tax system.^[2] The application is Form W-7 with documents proving foreign status and identity, generally with a federal income tax return attached unless an exception applies, sent by mail, presented at an IRS walk-in office, or handled through an IRS-authorized Acceptance Agent.^[1]

TIN is the umbrella term, and an EIN is one kind of TIN. The IRS lists five: the SSN, the EIN, the ITIN, the ATIN for pending US adoptions and the PTIN for tax return preparers.^[1] When a form asks for your TIN, it is asking for whichever of these applies to the person or entity named on it.

For a business the answer is usually the EIN. A single-member LLC is a common case that turns on the owner and the purpose: the SS-4 instructions say a disregarded entity uses its own name and EIN to report and pay employment taxes and certain excise taxes, and, where a US disregarded entity is wholly owned by a foreign person, to file Form 5472.^[3] For income tax, a disregarded LLC is treated as part of its owner; what a disregarded entity is explains how that works, and does an LLC get a 1099 covers which number goes on a W-9.

A US LLC owned by someone outside the US can get its EIN without the owner holding an SSN or ITIN. The SS-4 instructions say to enter “foreign” or N/A on line 7b if the responsible party does not have and is ineligible to obtain an SSN or ITIN.^[3] The online EIN application has two conditions of its own. The SS-4 instructions say the principal officer, owner or other responsible person “must have a valid taxpayer identification number (SSN, EIN, or ITIN) in order to use the online application”, and that an applicant with no legal residence, principal place of business, or principal office or agency in the US or US territories “can’t use the online application to obtain an EIN”.^[3] The IRS EIN page lists, for the online tool, “Your principal place of business is in the U.S. or U.S. territories” and the responsible party’s SSN or ITIN; for a principal place of business outside the US it says “apply by phone, fax or mail.”^[6] The telephone route is an option the IRS keeps for international applicants.^[3]

The owner's own number is a separate question. An owner who is not eligible for an SSN needs an ITIN when they personally have a federal tax purpose, such as being legally required to file a US federal income tax return.^[2] Our guides on the ITIN for LLC owners outside the US and the ITIN from Pakistan set out who needs one and what the W-7 application involves.

The company's Form 5472 and the owner's own US return are two separate questions. The Form 1040-NR instructions for 2025 list who must file, and the first case reads: “You were a nonresident alien engaged in a trade or business in the United States during 2025. You must file even if:” no income from a trade or business conducted in the US, “You have no U.S. source income”, or income exempt from US tax under a tax treaty or the Internal Revenue Code.^[7]

An owner who must file that return and can't get an SSN applies for an ITIN with it: Form W-7 reason box b covers a nonresident alien who must file a US federal tax return to report income effectively or not effectively connected with a US trade or business. The W-7 exceptions are for applications sent without a return, and the instructions say: “If you’re required to file a federal tax return, then you aren’t eligible for Exception 1.”^[8]

IRS Publication 519 says whether you are engaged in a US trade or business “depends on the nature of your activities”, and that if you “own and operate a business in the United States selling services, products, or merchandise, you are, with certain exceptions, engaged in a trade or business in the United States.”^[9] For an online seller, the answer turns on the facts. Our pages for owners outside the US and in Pakistan answer whether an LLC owes US income tax, and a written quote starts from your own facts.

If you are forming a US company from outside the US, our US LLC formation service files your articles of organization in the state you choose, arranges the registered agent in your quote and prepares the company's EIN application on Form SS-4, with every document kept in one folder.