ITIN vs SSN: what’s the difference, and which one do you need?
If you live in the U.S. and were never quite sure whether you need an ITIN, an SSN, or both — this guide settles it, with real cases and no jargon.
“Does my ITIN let me work?” “If I get an SSN, do I lose my credit history?” We hear these every week at our Austin office. The reality: the ITIN and the SSN are different tools — and knowing which one you need can save you thousands in mis-paid taxes or lost credits.
What each one is
The ITIN (Individual Taxpayer Identification Number) is a 9-digit number issued by the IRS so anyone with a U.S. tax obligation can file, whatever their immigration status. It does not authorize employment.
The SSN (Social Security Number) is issued by the Social Security Administration (SSA) to citizens, residents, and people authorized to work. It does authorize legal employment and opens access to federal benefits like Social Security and Medicare.
Neither replaces the other. That’s why it’s common to use an ITIN for years, then obtain work authorization or residency and switch to an SSN. For the full technical comparison, table by table, see our ITIN vs SSN page.
The quick comparison table
| ITIN | SSN | |
|---|---|---|
| What it’s for | Paying taxes | Working legally |
| Issued by | IRS | SSA |
| For whom | Anyone with a U.S. tax obligation | Citizens, residents, authorized workers |
| Authorizes work | No | Yes |
| Builds credit | Yes | Yes |
| Earned Income Tax Credit | No | Yes |
| Social Security benefits | No | Yes |
| Expires | Yes (3 years unused) | No |
5 real cases
Theory helps, but what people actually ask us about are concrete situations. Here are five we see all the time.
Case 1: María, arrived two years ago on a tourist visa
She works informally in cleaning and wants to file taxes to start building a record. She needs an ITIN, and can apply with her passport.
Case 2: Carlos, just received TPS
He used to file with an ITIN. His TPS (Temporary Protected Status) came with work authorization. He needs an SSN, and should notify the IRS so his tax history migrates to the new number.
Case 3: A mixed-status family — citizen dad, mom with an ITIN, citizen kids
Everyone has their own number, and they can still file jointly (Married Filing Jointly). Because the filing includes a spouse with an SSN and the kids have SSNs, the children qualify for the Child Tax Credit — a credit that doesn’t apply to dependents on an ITIN-only return.
Case 4: Ana, green card six months ago
She had an ITIN and had built credit history with it. On getting her SSN, she must notify the IRS in writing. Her ITIN goes inactive, but her credit history generally transfers to the new SSN once she updates her information with banks and bureaus.
Case 5: Luis, undocumented, wants to open an LLC
To open his Texas LLC, Luis needs neither an SSN nor an ITIN — the state doesn’t ask. But to file the LLC’s taxes, he does need an ITIN, which he can apply for together with his return.
Myths, dismantled
- “If I get an ITIN, immigration will deport me.” What the law says: Internal Revenue Code §6103 requires the IRS to keep your return information confidential, and the IRS does not routinely share it with USCIS. The law itself allows only narrow exceptions, such as a court order.
- “Credit built with an ITIN is useless.” False. There are credit cards, personal loans and even mortgages that accept an ITIN.
- “Paying taxes with an ITIN means admitting I’m here illegally.” False. The IRS doesn’t ask your immigration status. It just collects the taxes that are due.
- “Having an ITIN hurts a future green card.” The ITIN is a tax number, not an immigration record: the IRS created it precisely so you can meet your filing obligation. What weight your tax history carries inside an immigration case is a question for an immigration attorney — we don’t give immigration advice.
- “An SSN is always better than an ITIN.” Depends. For employment, yes. But if you don’t qualify for an SSN, the ITIN is the right tool for you — not a consolation prize.
What if I have both?
If you were issued an SSN after using an ITIN, you have to tell the IRS in writing so your records merge:
- Send the IRS a letter asking them to combine your records under your SSN.
- Your ITIN goes inactive (the IRS keeps it on file, but you shouldn’t use it again).
- Your tax and credit history transfers to your SSN.
- Use your SSN exclusively on future returns and with your creditors.
Can I switch from ITIN to SSN later?
Only if you qualify for an SSN — through TPS, asylum or residency, for example. The SSA doesn’t assign you an SSN “because you had an ITIN”: they’re two separate systems. Holding an ITIN neither speeds up nor delays your SSN application when the time comes.
Which one should I get?
Run through these in order:
- Are you a U.S. citizen? → You’re entitled to an SSN from birth.
- Do you have legal residency or work authorization? → Apply for your SSN with the SSA.
- Do you have a U.S. tax obligation but no work authorization? → You need an ITIN.
- No tax obligation and not working in the U.S.? → For now, you need neither.
What does each one cost?
The SSN is free if you qualify — you apply directly with the SSA. The ITIN is also free from the IRS: they charge nothing to issue it. What does carry a cost is the service of a Certified Acceptance Agent, and it depends on your case and whether the W-7 goes in with your return — we quote it in writing on your free consultation, before you decide anything.
Want help deciding, or filing your ITIN? Talk to an advisor → or see how it works entirely by mail → from any state.
Already have your ITIN and want to use it to build or repair your credit? Read our guide to credit with an ITIN.
