An ITIN is a personal tax ID for someone who has a US federal tax purpose but cannot get a Social Security number. It is not a requirement for owning a US LLC, forming one, getting an EIN, or opening a Mercury account. Most European founders do not need one at formation.
ITIN vs EIN vs SSN
| Number | Who it belongs to | Who issues it | Typical use for a European founder |
|---|---|---|---|
| EIN | The LLC | IRS | Banking, Form 5472, payroll, tax accounts. Usually needed. |
| ITIN | An individual | IRS | A US individual tax return, a treaty claim, certain withholding or reporting. Needed only when you have a federal tax purpose. |
| SSN | An individual with US work authorisation or another qualifying status | Social Security Administration | Not available merely because you own a US LLC. |
When you actually need an ITIN
The IRS says an ITIN is for someone who has a federal tax purpose and is not eligible for an SSN. Common examples for a foreign LLC owner include filing a US nonresident individual return (Form 1040-NR) to report US-source income, claiming a treaty benefit that requires an ITIN, or being listed on a US return because of a US trade or business. The IRS also warns that a tax return with all zero entries generally does not show a federal tax purpose.
Owning a single-member LLC that is disregarded for US federal income tax is not, by itself, an ITIN trigger. The LLC's federal information return is Form 5472 plus a pro forma Form 1120, and the EIN is the relevant number. If the LLC has US-source income that is effectively connected with a US trade or business, or if you have another US filing reason, an ITIN may become relevant. That is a facts-and-circumstances question for a US accountant.
The W-7 package
Form W-7 is the application. For a first-time ITIN, the IRS generally requires the completed W-7, a US federal tax return for which the ITIN is needed, and original or certified supporting documents proving identity and foreign status. A passport is the most common document; if you send it, the IRS returns it. You can also apply through an IRS-authorised acceptance agent or at a designated Taxpayer Assistance Center.
The return is normally attached to the front of the W-7 package, not filed separately. If you are applying for a prior-year return or meet an exception, you may be able to apply without attaching a current return. The W-7 instructions list the exceptions and the document rules in detail. Do not send a photocopy of a passport unless the instructions specifically allow it.
How long it takes
The IRS says to allow seven weeks for notification of an ITIN application status, or nine to eleven weeks if you apply during the peak period from 15 January to 30 April, or from overseas. That is processing time, not a guaranteed end-to-end timeline. Post, document review and a missing signature can add weeks.
If you need the ITIN for a return due date, plan backwards. The IRS says you must have the ITIN assigned by the return due date (including extensions) to claim certain credits. An extension to file is not an extension to pay, and you do not need an ITIN to request an extension or make an estimated payment.
Do not apply “just in case”
An unnecessary ITIN application costs time, may require you to send original documents, and can create confusion if you later become eligible for an SSN. The IRS says you should not complete Form W-7 if you have an SSN or are eligible for one. If you have an SSN application pending, do not file a W-7 in parallel; wait for the Social Security Administration's decision.
If you already have an ITIN, check whether it has expired. The IRS says an ITIN that was not included on at least one federal tax return for three consecutive years expires on 31 December of the third year. Renewal normally requires a return unless an exception applies. An expired ITIN can delay a refund or a return.
What it costs
The IRS does not sell the ITIN, but the application can involve real costs: certified copies of documents, courier fees, translations, and an acceptance agent's service fee if you use one. Those fees vary and are not published as a single official price, so this guide does not invent a number. Ask for a written quote and check whether it includes the IRS submission, document return and follow-up.
If you are in the Netherlands or Poland
Your local tax office does not issue a US ITIN, and a Dutch or Polish tax number cannot substitute for one on a US return. If a US accountant tells you that you need an ITIN, ask which US return or treaty benefit creates the requirement, and get the answer in writing. That sentence will save you from applying for a number you do not need.
Questions
Frequently asked
Do I need an ITIN to form a US LLC?
Do I need an ITIN to open a US business bank account?
Can I get an ITIN without filing a US tax return?
How long is an ITIN valid?
Is an ITIN the same as a US tax residency?
Sources and checks
All figures on this page were checked on 22 October 2026. A link is not an endorsement; it is where the number or rule comes from.