You need an ITIN for your tax return if the IRS requires you to file or be listed on a return, and you're not eligible for a Social Security Number. This is separate from whether you owe tax — many ITIN holders file simply to report income or claim a treaty benefit.
Situations that typically require an ITIN
- You're a non-resident alien who must file a U.S. return for income earned here.
- You're a resident alien (based on days present in the U.S.) filing a return.
- You're a dependent or spouse of a U.S. citizen or resident alien, without SSN eligibility.
- You're a non-resident alien claiming a tax treaty benefit.
What if I already filed without one?
You can submit Form W-7 together with your tax return even after the filing deadline has passed, though this may affect certain credits that have their own ITIN-by-deadline rules. It's worth getting this right rather than guessing — an incorrect reason code is one of the most common rejection causes.
ITIN vs. SSN vs. EIN — which do you actually need?
An ITIN is only for individuals filing taxes who can't get an SSN. If you're starting a business, you may instead need an EIN, which identifies the business itself, not a person.
