If you’re working, investing, or living in the US, you likely need a US taxpayer identification number (TIN). But which one? And how do you get it? This guide walks you through the main types of taxpayer ID numbers — including when to use them, who qualifies, and how to apply — with insider tips you won’t find on the IRS website.
Do I Need a Taxpayer ID Number?
Yes — if you are interacting with the US tax system in any way, you likely need a TIN. Here’s when a TIN is required:
You must provide a TIN when:
- Filing your US tax return
- Claiming tax treaty benefits
A TIN is also required on a withholding certificate if you’re claiming:
- Tax treaty benefits (other than for income from marketable securities)
- Exemption for income effectively connected with a US trade or business
- Exemption for certain U.S.-source annuities
Example 1: Say you’re a foreign individual who just acquired rental property in the US. You now have US-source income and must file a federal (and possibly state) tax return each year. If you don’t have an SSN, you’ll need to apply for an ITIN to report your rental income.
Example 2: If you’re a nonresident selling US real estate, the FIRPTA rules require the buyer to withhold 15% of the gross sales proceeds and remit it to the IRS. This amount often exceeds the actual tax owed on the gain. To claim a refund of the excess withholding (or to apply in advance for a reduced rate via Form 8288-B), you’ll need a valid ITIN to file a US tax return.
Without a valid TIN, forms may be rejected, refunds delayed, or treaty benefits denied.
What Is a US Taxpayer ID Number?
A Taxpayer Identification Number (TIN) is a unique number used by the IRS to track taxpayers for reporting and filing purposes. There are five main types:
- SSN – Social Security Number (issued by SSA)
- ITIN – Individual Taxpayer Identification Number
- EIN – Employer Identification Number
- ATIN – Adoption Taxpayer Identification Number
- IRSN – IRS-issued placeholder when no TIN is available
You need a TIN to file US tax returns, claim tax treaty benefits, open bank accounts, and more.
Summary Table: Which ID Number Do You Need?
| You are… | Use this ID number |
|---|---|
| A US citizen, green card holder, tax resident, or visa holder with work authorization | SSN |
| A foreign national who is not eligible for an SSN | ITIN |
| A business, trust, or estate | EIN |
| A foreign buyer/seller of US property | ITIN |
| Adopting a US child without an SSN | ATIN |
| Filed a return with no ID | IRSN (temporary only – IRS assigned) |
SSN – Social Security Number
Issued by the Social Security Administration (SSA), the SSN is used by US citizens, green card holders, tax residents, and individuals on L-1, H-1B, and certain J, F, M, or Q visas — if authorized to work in the US.
To apply: File Form SS-5 with the SSA. If applying abroad, contact a US embassy or consulate with a Federal Benefits Unit.
Tip: US citizens abroad may also be eligible for up to $1,700 per child under age 17 through the Additional Child Tax Credit (ACTC) — but only if each child has a valid SSN and the parents are not claiming the Foreign Earned Income Exclusion (FEIE).
ITIN – Individual Taxpayer Identification Number
For individuals not eligible for an SSN — such as nonresidents, spouses, dependents, or foreign investors — the IRS issues an ITIN.
To apply: Submit Form W-7 with a tax return (unless qualifying for an exception), plus original/certified documents proving identity and foreign status.
Use cases:
- Nonresidents with US rental income
- Foreign sellers of US real estate
- Dependents/spouses of US taxpayers
- Treaty claims by individuals not eligible for SSNs
Tip: Filing with an ITIN allows you to claim the $500 Other Dependent Credit (ODC) for eligible dependents (including some children and relatives), but not the Earned Income Credit or the Child Tax Credit. The ODC is nonrefundable and phases out at $400,000 MAGI for joint filers and $200,000 for others. The dependent must be a resident alien and have an ITIN issued by the return due date.
Check out our full ITIN guide
EIN – Employer Identification Number
An Employer Identification Number (EIN) is used to identify businesses, estates, and trusts for tax purposes in the U.S. You’ll need an EIN if you plan to hire employees, open a U.S. business bank account, file business tax returns, or claim tax treaty benefits on forms like W-8BEN-E.
To apply:
- US entities can apply online via the IRS EIN Assistant
- File Form SS-4 by fax or mail
International EIN applicants:
If your principal place of business is outside the US, you can apply for an EIN by phone at 267-941-1099 (Monday–Friday, 6 am to 11 pm Eastern time) or submit Form SS-4 by:
- Fax: 855-215-1627 (within the US) or 304-707-9471 (outside the US)
- Mail: Internal Revenue Service, Attn: EIN International Operation, Cincinnati, OH 45999
Note: Only one EIN application per day is allowed per responsible party, regardless of the method used.
ATIN – Adoption Taxpayer Identification Number
An ATIN is a temporary taxpayer ID number issued by the IRS for US children in the process of being adopted domestically, when an SSN is not yet available and the adoptive parents need to claim the child on a tax return.
To apply: File Form W-7A with supporting adoption documents.
Note: Foreign children being adopted who are not US citizens or residents generally don’t qualify for an SSN yet, so parents apply for an ITIN instead — not an ATIN.
IRSN – Internal Revenue Service Number
This is a temporary placeholder number the IRS uses if a return is filed without a valid TIN.
- It looks like an ITIN (starts with “9”) but can’t be used for future filings.
- It may appear on IRS notices and can be referenced in correspondence.
- Not eligible for credits, refunds, or e-filing.
Example: A former US citizen filing under Relief Procedures may file without an SSN — the IRS assigns an IRSN to process the return
Special Visa Situations
Holders of J, F, M, or Q visas must:
- Apply for an SSN if authorized to work
- Apply for an ITIN if not eligible for an SSN but required to file or be listed on a return
Key points:
- An SSN is always preferred if available
- The IRS will reject ITIN applications if the applicant is eligible for an SSN
FAQ: SSN and ITIN Practical Issues
- When and why do ITINs expire?
If not used on a tax return for 3 years or based on older middle-digit expiration cycles. - How to renew an ITIN?
File Form W-7 with ID documents, checking the “Renewal” box. No return needed. - Can you file with an expired ITIN?
Yes, but refunds/credits will be delayed or denied until renewal. - What if you get an SSN after having an ITIN?
Notify the IRS and use the SSN going forward. They’ll merge your records. - Can you use an expired ITIN on Form 1099?
Yes. Third parties can still file 1099s with expired ITINs. - Does having an ITIN affect your credit?
Not directly — credit bureaus use SSNs primarily. Tax info isn’t shared. - What if you’re eligible for an SSN but apply for an ITIN?
The IRS will deny your ITIN and ask for SSA confirmation. - Can family members renew their ITINs together?
Yes. If one ITIN needs renewal, the whole household may apply together. - Can you renew before expiration?
Yes. You don’t need to wait for an IRS notice. - Do ITINs allow work or Social Security benefits?
No. ITINs are for tax reporting only.
Final Thoughts
Choosing the right taxpayer ID number helps avoid delays, penalties, and confusion with the IRS. Whether you’re a parent, investor, business owner, or expat — the correct TIN gets you in the system and keeps you compliant.
Need help applying for an ITIN?
Contact us — we specialize in helping expats, international investors, and global families navigate the US tax system with confidence.