Four abbreviations circulate in the same conversations, and one of them is not a number at all. Sorting them out takes a minute and prevents the most expensive mistake in this area: applying for the wrong one.
What does each abbreviation mean?
Three numbers, one umbrella term. Each of the three answers a different question: who is this business, who is this worker, who is this filer without work authorisation.
| Term | Identifies | Issued by | Applied for with |
|---|---|---|---|
| SSN | An individual authorised to work in the United States | Social Security Administration | Form SS-5 |
| ITIN | An individual with U.S. tax obligations who cannot obtain an SSN | IRS | Form W-7 |
| EIN | A business, trust, estate or other entity | IRS | Form SS-4 |
| TIN | Nothing on its own — the umbrella term for all of the above | — | — |
Descriptions checked against IRS material in August 2026. TIN appears on forms and in instructions as a category, which is why a request for "your TIN" is answered with whichever of the three actually applies to you.
Which number does my situation call for?
Match the number to the party being identified, not to the person filling in the form. That single rule resolves most of the confusion.
| Your situation | The number you need |
|---|---|
| Registering a company, trust or estate | EIN |
| Hiring employees | EIN for the business |
| Filing a personal U.S. return without work authorisation | ITIN |
| Claiming a treaty rate on U.S.-source income as a foreign individual | Often a foreign tax number, sometimes an ITIN |
| Opening a business bank account | EIN, in practice, whatever tax law requires |
Does an ITIN come before an EIN?
No, and the assumption that it does costs foreign founders weeks. The two numbers are independent: an entity may receive an EIN while its responsible party holds no U.S. number whatsoever. 1
Line 7b of Form SS-4 accepts the word Foreign precisely for that case. What the missing number does change is the channel — paper or phone instead of the online assistant — which is set out in how to get an EIN without an SSN or ITIN. 1,2,3
What does an ITIN not do?
An ITIN exists for federal tax reporting and nothing else. The IRS page on ITINs is explicit about the boundary, and marketing that suggests otherwise is inventing benefits.
Four things it does not provide: work authorisation, immigration status, eligibility for Social Security benefits, and a personal credit history. Some banks accept an ITIN as identification when opening an account, which is a decision by that bank rather than a right attached to the number.
What if I hold none of them?
Holding nothing is a normal starting position for a foreign founder, and it does not block a business from getting its EIN. The entity applies on paper, the responsible party is named without a number, and the IRS issues the same EIN it issues to everyone else. 1,2,3
Whether an individual then needs an ITIN is a separate question, answered by their own filing obligations rather than by the company's. Deciding that the company needs a number is the first step, and do you actually need an EIN? covers it.