What Is an A-Number (Alien Registration Number) and Where to Find It
Updated November 1, 2026. Sources: USCIS.gov.
Not legal advice. GreenCardBlog.com is an independent information site, not a law firm and not affiliated with USCIS or any government agency. Immigration rules, fees and timelines change. Always confirm details on USCIS.gov and consider speaking with a licensed immigration attorney about your situation.
Short answer: an A-Number (also called an Alien Registration Number or A#) is a unique seven-, eight- or nine-digit number that the Department of Homeland Security assigns to a noncitizen. It stays with you across cases, so USCIS forms ask for it whenever you have one. Source: USCIS glossary.
Where to find your A-Number
- Green card: on Permanent Resident Cards issued after May 10, 2010, the 9-digit number on the front labeled USCIS# is your USCIS Number, which is the same as your A-Number (USCIS glossary).
- USCIS notices and prior applications: if you had a case where an A-Number was assigned, check the notices and copies of forms you filed.
- Your immigration file: if you cannot find it anywhere, you can request your records from USCIS through a FOIA or Privacy Act request.
A-Number vs. other USCIS numbers
| Number | What it is | Where you see it |
|---|---|---|
| A-Number (A#) | 7 to 9 digits; assigned to you as a person by DHS | Green card (USCIS#), USCIS notices, forms you filed |
| Receipt number | Identifies one case or application, not you | Form I-797 receipt notices; used to check case status |
| USCIS Online Account Number (OAN) | Identifies your USCIS online filing account; USCIS says it is not the same as an A-Number | Your online account profile, or the Account Access Notice if you filed on paper |
Tips when filling out forms
- Only enter an A-Number if DHS actually assigned you one. Many first-time applicants do not have one yet, and forms say "if any".
- USCIS form instructions ask you to write your name and A-Number (if any) at the top of extra sheets and lightly on the back of passport photos (Form I-485 instructions).
- Do not guess or reuse someone else's number; a wrong number can slow your case.
FAQ
Is the USCIS# on my green card my A-Number?
Yes. USCIS defines the USCIS Number on cards issued after May 10, 2010 as a 9-digit number assigned by DHS, and cross-references it to the A-Number.
Is my receipt number my A-Number?
No. A receipt number tracks one application; your A-Number follows you across all of them.
I lost my green card. How do I get my number?
Check copies of old notices and forms first. To replace the card, see our green card replacement guide.
Related: I-485 processing time, green card document checklist and how to find a green card lawyer.
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