People apply for the wrong one, wait seven weeks, and find it does not do what they needed. The distinction is simple once stated.
Three numbers, often confused.
| What it identifies | Who gets it | Issued by | |
|---|---|---|---|
| SSN | An individual | US citizens and work-authorised non-citizens | Social Security Administration |
| ITIN | An individual | People needing a US tax ID who are not eligible for an SSN | IRS |
| EIN | An entity | Businesses, trusts, estates | IRS |
Issued by the Social Security Administration to citizens and to non-citizens authorised to work. It is the identifier for employment, for Social Security benefits, and for most of US financial life.
If you are eligible for an SSN, you cannot have an ITIN. The ITIN exists only for people who are not eligible.
A nine-digit number the IRS issues, in its own words, "if you need a U.S. taxpayer identification number for federal tax purposes, but you aren't eligible for a Social Security number."
Who can get one: resident aliens, nonresident aliens, and their spouses and dependants — regardless of immigration status. That last point matters and is widely misunderstood.
What it does not do. This is the important list:
An ITIN is a filing number. Nothing more.
How to apply: Form W-7, normally filed with your tax return. Processing takes about seven weeks, or nine to eleven weeks during filing season or for applicants abroad.
Expiry: "If an ITIN isn't used on a U.S. federal tax return for any 3 consecutive tax years, it expires on December 31 after the third tax year of non-use." An ITIN used within the past three years stays valid. Renew by submitting Form W-7 with "Renew an existing ITIN" ticked.
An expired ITIN may still be used on information returns such as 1099s without renewal.
One caution: older guidance about batches of ITINs expiring by middle digits circulates widely online. The current IRS page states only the three-consecutive-years rule. Do not rely on the batch lists.
An entity-level federal tax ID. You need one to open a US business bank account, to hire employees, to file a Form 5472 for a foreign-owned LLC, and for most payment processors.
It is free, and international applicants can get one by phone the same day without an SSN or ITIN. Full detail in how to get a US EIN in 2026.
The key point worth repeating here: the requirement to hold an SSN or ITIN applies only to the online application. Apply by phone or fax as an international applicant and you enter "Foreign" where a US tax ID would go.
Working in the US with authorisation → SSN, from the SSA.
Filing a US return but not eligible for an SSN → ITIN, on Form W-7 with your return.
A spouse or dependant being claimed on a US return, not eligible for an SSN → ITIN.
Opening a US business or filing for a US entity → EIN for the entity. You may need nothing personally.
A non-resident forming a US LLC → EIN for the LLC. You do not need an ITIN first, despite what a lot of online guidance says.
That last case is the one that costs people the most time. The advice to "get an ITIN first" sends non-residents into a seven-week process they do not need before a same-day phone call they do.