What Is the Difference Between a TIN, SSN, and ITIN?
A Taxpayer Identification Number (TIN) is the umbrella term for any number used to identify a taxpayer on U.S. tax returns. A Social Security Number (SSN) is issued to U.S. citizens and authorized workers. An Individual Taxpayer Identification Number (ITIN) is issued to individuals who are ineligible for an SSN but need to file a U.S. tax return (IRS: Taxpayer Identification Numbers).
| Feature | SSN | ITIN |
| Issued by | Social Security Administration | IRS |
| Format | 9 digits (XXX-XX-XXXX) | 9 digits starting with 9 (9XX-XX-XXXX) |
| Who gets one | U.S. citizens, permanent residents, authorized workers | Anyone ineligible for an SSN who needs to file a U.S. return |
| Application form | SS-5 | W-7 |
| Expires? | No | Yes, if not used on a return for 3 consecutive years |
| Authorizes work? | Yes | No |
When expats need each:
- SSN: U.S. citizens already have one. If your child was born abroad, apply for an SSN through a U.S. Embassy or consulate before filing their first return.
- ITIN: your foreign spouse needs one to file a joint return under Section 6013(g). Your foreign-born dependent may also need one if ineligible for an SSN.
- EIN (Employer Identification Number): a type of TIN for businesses, trusts, and estates. Not interchangeable with SSN or ITIN for personal returns.
How to apply for an ITIN:
- File Form W-7 with the IRS, attaching it to your tax return
- Include identity documents: passport, national ID card, or other approved documentation
- Processing time: 7 to 11 weeks; apply early in the filing season
- Certified Acceptance Agents (CAAs): can verify your documents, so you do not need to mail originals
- Renewal: ITINs that have not been used on a return for 3 consecutive years expire and must be renewed before filing
For more on getting an ITIN for a foreign spouse, see our Filing Joint Taxes with a Foreign Spouse guide.
Last updated on April 29, 2026
