If you are a Korean entrepreneur doing business in the US but do not qualify for a Social Security Number, the ITIN application process is likely on your radar. An ITIN, or Individual Taxpayer Identification Number, lets people who are not eligible for an SSN meet US tax filing and reporting requirements. This guide walks through who needs one, what documents you need, and how to submit your application without common delays.
What an ITIN Is and Who Needs One
An ITIN is a nine-digit number issued by the IRS for tax purposes only. It always begins with the number nine. It does not grant work authorization, does not provide immigration status, and does not make you eligible for Social Security benefits. Its single purpose is to identify individuals in the US tax system who cannot get an SSN.
You may need an ITIN if you are a nonresident who must file a US tax return, a foreign owner of a US company with a reporting obligation, a partner in a US partnership, or someone claiming a tax treaty benefit. Many founders discover they need an ITIN when their US entity generates income that must be reported, or when a bank, marketplace, or payment processor requests a US taxpayer number.
It is important to understand that an ITIN is for individuals. A company uses an Employer Identification Number (EIN) instead. The two are often confused, so make sure you are applying for the right identifier for the right purpose.
Form W-7: The Core of the ITIN Application
The heart of any ITIN application is Form W-7, the official request for an Individual Taxpayer Identification Number. On this form you state the reason you need an ITIN, provide your identifying information, and describe your foreign status. Choosing the correct reason category is essential, because an incorrect or unsupported reason is a frequent cause of rejection.
In most cases, Form W-7 must be attached to a completed US federal tax return. The IRS wants to see the tax purpose behind your request. There are exceptions, such as certain treaty claims or third-party reporting situations, where you can apply without a return, but you must document the exception clearly.
Documents You Need to Prove Identity
The IRS requires proof of both your identity and your foreign status. A valid passport is the single document that satisfies both requirements on its own, which is why most applicants rely on it. If you do not use a passport, you must provide a combination of other documents, such as a national identification card and a foreign driver’s license.
Here is the catch that trips up many applicants: the IRS does not accept plain photocopies. You must submit either:
- Your original documents, or
- Copies certified by the issuing agency, or
- Documents verified by an IRS-authorized Certifying Acceptance Agent (CAA).
Mailing an original passport abroad is understandably nerve-wracking. This is why many overseas founders work with a Certifying Acceptance Agent, who can verify identity documents so you do not have to part with your passport. It adds a step but greatly reduces risk and often speeds up processing.
How to Submit Your Application
There are three main ways to file an ITIN application:
- By mail: Send Form W-7, your tax return, and original or certified documents to the IRS ITIN processing address.
- Through a Certifying Acceptance Agent: A CAA reviews and certifies your documents, then forwards the application, so you keep your originals.
- In person at an IRS Taxpayer Assistance Center: Available by appointment, though limited for applicants outside the US.
For founders based in Korea, the CAA route is usually the most practical because it removes the need to mail a passport across the world. Fees for these services vary, so ask for a clear quote before you commit.
Timeline, Renewals, and Common Mistakes
Processing time varies and can stretch longer during peak tax season, so apply well before any deadline. Once issued, the number stays with you, but an ITIN can expire if it is not used on a federal tax return for several consecutive years. If yours has expired, you will need to renew it before filing again, which uses the same Form W-7 process.
Common mistakes that cause delays or rejection include:
- Selecting the wrong reason for applying.
- Sending uncertified photocopies of documents.
- Leaving off the required tax return when no exception applies.
- Name mismatches between the form and the identity documents.
- Using an expired passport as proof.
Double-checking each of these before you submit can be the difference between a smooth approval and months of back-and-forth. Keep copies of everything you send and any tracking information.
Why the ITIN Matters for Your US Business
For many foreign founders, the ITIN is the key that unlocks proper tax compliance. It lets you file returns you are required to file, claim treaty benefits you are entitled to, and respond correctly when a US institution asks for a taxpayer number. Handling it early, rather than under deadline pressure, keeps your US operation on solid footing and signals that your business takes compliance seriously.
Frequently Asked Questions
Does an ITIN let me work in the US?
No. An ITIN is strictly for tax reporting and filing. It does not authorize employment, provide any immigration benefit, or replace a work visa or Social Security Number.
Can my company use an ITIN instead of an EIN?
No. An ITIN is for individuals only. A business entity uses an Employer Identification Number. If you need a number for your company, apply for an EIN rather than an ITIN.
Do I have to mail my original passport for the ITIN application?
Not necessarily. If you use a Certifying Acceptance Agent, they can verify your passport so you keep the original. Otherwise you would need to send the original or an agency-certified copy.
This article is general information, not legal or tax advice; please consult a qualified professional for your situation. If the ITIN application process feels overwhelming, we can help you prepare and file it correctly. USdongsan offers a free consultation to guide you through your ITIN application and broader US tax setup.
