Form I-797 Notice of Action explained - I-797, I-797A, I-797B, and I-797C
8 mins read | Jun 29, 2026
An Alien Registration Number, usually written as A-Number or "A#," is the unique identifier the U.S. government assigns to track your immigration file. If you're holding a green card, an Employment Authorization Document, or a letter from USCIS and you've been asked for your A-Number, this guide shows you what the number means, what it's used for, and exactly where to find it on each document.
Think of the Alien Registration Number as the case number that follows you through the entire immigration process. The same A-Number stays with you from your first petition to your green card and, eventually, to naturalization. It never changes, even when your visa status does.
What is an Alien Registration Number?
The Alien Registration Number is a unique 7 to 9 digit number that the Department of Homeland Security uses to identify a foreign national and link every record tied to that person. You'll often see it printed with an "A" in front, such as "A123456789." Older files used seven or eight digits, while USCIS now issues nine-digit A-Numbers, sometimes shown with leading zeros to fill out the nine places.
Not everyone in the immigration system has one. USCIS typically assigns an A-Number when you file certain applications, when you apply for an immigrant visa, or when you receive work authorization. Many people first encounter their A-Number on an approval notice or on the card that grants them a benefit, which is why the number can feel like it appeared out of nowhere.
Because it's tied to your record rather than to a single application, the A-Number is one of the few constants in an otherwise document-heavy process. Your receipt numbers change with each filing and your visa stamp expires, but your Alien Registration Number stays the same.
What the A-Number is used for
Your A-Number lets USCIS, the immigration courts, and other agencies pull up your complete immigration history in one place. When an officer reviews a new petition, the A-Number connects it to everything already on file, from prior approvals to biometrics to past entries on your I-94 arrival record.
You'll be asked for the Alien Registration Number on most major immigration forms, including the green card application and renewal forms, work permit applications, and travel documents. Attorneys use it to file a notice of appearance, and the immigration court uses it as your docket reference if your case is ever heard before a judge.
For day-to-day purposes, the most common reason people look for their A-Number is to complete a new form or to verify their identity with an employer or a government agency. Entering the wrong number, or confusing it with a different identifier, can delay your case or trigger a request for evidence, so it's worth knowing exactly where yours lives.
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Where to find your Alien Registration Number on each document
Your Alien Registration Number appears on nearly every official document USCIS issues to you, though it isn't always labeled the same way. The fastest place to look depends on which documents you currently hold, so here's where the A-Number sits on each one.
A-Number on a green card (Permanent Resident Card)
On a current Permanent Resident Card, your A-Number is printed on the front and labeled "USCIS#." It's the same nine-digit number as your A-Number, just shown without the "A" prefix. Older green cards may label this field "A#" instead. This is also what people mean when they ask for the permanent resident card number tied to your status. USCIS describes the card's fields on its official green card page.
A-Number on an EAD (work permit)
If you have an Employment Authorization Document, the card issued after you file Form I-765, your A-Number appears on the front, again labeled "USCIS#." The EAD also shows a separate card number, but that's not your A-Number. For a full walk-through of how the work permit is issued, see our Form I-765 guide.
A-Number on an immigrant visa and USCIS notices
When you receive an immigrant visa in your passport through consular processing, the A-Number is printed in the "Registration Number" field. It also appears in the upper-left area of most USCIS notices, including Form I-797 approval and receipt notices, and on any request for evidence or notice of intent to deny you receive. If you've been issued an I-94 arrival record tied to immigrant status, you may see it referenced there as well; our guide to the I-94 form explains that record in detail.
| Document | Where the A-Number appears | How it's labeled |
|---|---|---|
| Permanent Resident Card (green card) | Front of the card | USCIS# (older cards: A#) |
| Employment Authorization Document (EAD) | Front of the card | USCIS# |
| Immigrant visa | Passport visa page | Registration Number |
| Form I-797 notices | Upper-left section | A# |
| RFE / NOID letters | Top of the letter | A# |
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A-Number vs USCIS online account number vs receipt number
The Alien Registration Number is easy to mix up with two other identifiers, but each one does a different job. Getting them straight matters, since forms ask for specific numbers and entering the wrong one can stall your case.
The USCIS online account number is a 12-digit number tied to your myUSCIS online account, not to your immigration file. USCIS sends it in a notice when you create an account or when a paper filing gets linked to one. You only need it if you're managing your case online, and it has nothing to do with your A-Number.
The receipt number is a 13-character code, made up of three letters followed by ten digits, such as "IOE0123456789" or "WAC2212345678." Unlike the permanent A-Number, a receipt number is generated for each individual application you file, so you'll have a different one for every petition. You use it to track a specific case, which you can do through our guide to checking your USCIS case status.
In short, your A-Number identifies you, the receipt number identifies a filing, and the online account number identifies your myUSCIS login. When a form asks for the Alien Registration Number, it wants the number that follows your file, not the case-specific receipt number.
What to do if you can't find your A-Number
If none of your documents show an A-Number, the most likely reason is that one hasn't been assigned to you yet. People in earlier, nonimmigrant stages of the process, such as a tourist or some temporary work classifications, often don't have an Alien Registration Number until they apply for a green card or work authorization. In that case, you can leave A-Number fields blank or mark them "N/A" unless a form specifically requires one.
If you believe you should have an A-Number but can't locate it, check older USCIS notices and any approval letters first, since the number appears on most of them. You can also request your records from USCIS through its records request process, or speak with an immigration attorney who can help confirm your number before you submit a new filing. When you later apply for permanent residence, the A-Number becomes a standard field, as explained in our overview of Form I-485.
Keeping your A-Number somewhere safe saves time later. You'll reuse it when you renew your green card, apply for travel documents, or eventually file for citizenship, so it's worth recording once you have it.
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