An ITIN is a tax processing number, and it exists for one reason: so that somebody who has a US tax obligation but cannot get a social security number has a way to file. That is the whole of its purpose. It is not an identity document, it does not authorise work, it does not change immigration status, and it gives you no entitlement to social security benefits.
It is also the thing most likely to be sitting between a newly arrived family and their first return, so it is worth getting right the first time.
Who needs one, and who should not apply
You may need an ITIN if you have a federal tax purpose and are not eligible for a social security number. In practice that is usually:
- A nonresident with a US filing obligation
- A spouse or a dependent being claimed on someone else’s return
- A student, professor, or researcher whose visa status does not come with work authorisation
- Somebody claiming a treaty benefit
You are not eligible, and should not apply, if you can get a social security number. That rules out US citizens, green card holders, and people on work visas that carry work authorisation, who should apply for an SSN instead. Applying for an ITIN when you are SSN eligible is a wasted application.
The limits are worth stating plainly, because people assume the number does more than it does. An ITIN does not qualify you for the earned income tax credit, and it does not qualify you for social security benefits. Some credits are available to ITIN holders and some are not, and which is which changes, so it is a thing to check in the year you are filing rather than to assume.
The application is not a standalone form
This is the first thing people get wrong about the process. Form W-7 is not sent in on its own and answered in due course. It is generally filed together with the tax return it is needed for, with the social security number field on that return left blank.
So the sequence is not “get the number, then file”. It is “file, with the application attached, and the number is issued as part of processing it”. Which return that is depends on your residency status rather than your visa, and that question comes first. There are exceptions where a return is not required, but the default is that the return and the application travel together.
Why applications get refused, and it is nearly always the documents
The documentation rule is strict and it is the single largest cause of rejection.
Supporting documents must be originals, or certified copies from the issuing agency. A certified copy has to come from the agency that issued the document in the first place, and it has to carry that agency’s official stamped seal.
A notarised copy is not acceptable. A notary is not the issuing agency, and this is where a great many applications fail, because taking documents to a notary is what most people would reasonably assume is wanted. The narrow exception is for dependents and spouses of US military personnel stationed overseas, who may submit notarised copies.
Two further points from the instructions that cost people weeks:
- The passport is the only document that stands alone. Submit a valid original passport, or a certified copy from the issuing agency, and nothing else is needed to establish both identity and foreign status. Everything else requires a combination. The exception is a dependent who has to prove US residency, where a passport works alone only if it shows a date of entry.
- Quality and consistency matter. Documents that are unclear or blemished are likely to be treated as invalid, and names, addresses, and dates have to match across everything submitted. A middle name present on one document and absent on another is a real reason for a delay.
The part nobody warns you about
If you apply by post with original documents, your passport leaves your possession. The published guidance is to allow seven weeks for notification, rising to nine to eleven weeks if you apply during filing season or from overseas.
For most people that is unacceptable. There are routes that avoid it:
- An IRS Taxpayer Assistance Centre, which can verify documents in person, at no charge
- A VITA site that offers ITIN services, also free
- An Acceptance Agent or Certifying Acceptance Agent, who charge a fee
A Certifying Acceptance Agent can authenticate most supporting documents at the appointment, so the originals stay with you. There are limits: they cannot authenticate foreign military identity documents, and for dependents they can only authenticate passports and birth certificates. Anything outside that still has to be posted.
If you have any plan that needs your passport in the next three months, settle this before you apply rather than afterwards.
ITINs expire, and people are caught by it
An ITIN is not permanent once issued. If it is not used on a US federal tax return for three consecutive tax years, it expires on 31 December of that third year.
The effect is delayed and quiet. Somebody files for two years, has a few years where no return is required, comes back to file, and finds the number they have written on the form is dead. The return is processed with problems, credits can be disallowed, and a refund is reduced or held.
One clarification that matters, because it is easy to misread the rule. Use on an information return does not count. If your ITIN appears only on something like a Form 1099 reporting payments to you, that does not keep it alive. The test is whether it was used on a federal tax return.
Renewing is another Form W-7, with the application type marked as a renewal, and the same documentation rules apply. Renew before filing season rather than during it.
What to do, in order
- Check that you are genuinely not eligible for a social security number, because if you are, this is the wrong form.
- Prepare the return the ITIN is needed for, leaving the number field blank.
- Decide your document route before anything else. If you need to keep your passport, book a Taxpayer Assistance Centre appointment or find a Certifying Acceptance Agent.
- Check the documents against each other for consistent names, addresses, and dates, and make sure nothing is expired or unclear.
- If this is a renewal, deal with it early rather than in April.
Applications on Form W-7 are quoted separately rather than folded into a return fee, and what the international work does cover is set out there.