Filing Guide · Updated July 2026

What is an A-number? Where to find your Alien Registration Number on every document

One number, several names, and half a dozen documents it hides on. Here is how to find yours, and what to do if you don’t have one yet.

The short answer

An A-number (Alien Registration Number) is the 7-, 8-, or 9-digit file number the Department of Homeland Security assigns to an immigrant, written as an “A” followed by the digits. On a green card or work permit it is printed on the front as “USCIS#.” It identifies you, permanently; it is not your receipt number, your online account number, or your Social Security number.

At a glance

•What it looks like: “A” plus 7 to 9 digits, like A012345678.
•Fastest place to find it: the “USCIS#” on the front of a green card or work permit.
•International student (F-1) with a post-study work card (an OPT EAD)? The USCIS# printed on that card is your A-number.
•Never had a USCIS card or case? You probably don’t have one yet; the forms say to write “N/A.”
•It is not your case number. Receipt numbers (3 letters + 10 digits) track a case; the A-number tracks you.

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What an A-Number Actually Is

The USCIS glossary defines the A-number as “a unique seven-, eight- or nine-digit number that the Department of Homeland Security assigned to an alien.” Think of it as your permanent file number in the immigration system: applications come and go, each with its own case number, but the A-number stays attached to you and your records across all of them.

The I-765 work permit instructions put its purpose in one sentence: “We use your A-Number to identify your immigration records. It begins with an ‘A’ and can be found on correspondence you have received from the Department of Homeland Security (DHS) or USCIS.”

On paper the number is written with the letter A in front: A12345678 or A012345678. On plastic cards the A is dropped and the digits appear next to the label “USCIS#.” That renaming trips up more people than anything else about this number, so let’s deal with it first.

Is the “USCIS#” on My Card the Same as My A-Number?

Yes, for green cards and work permits. USCIS’s glossary defines the USCIS Number as “a unique, 9-digit number assigned to an alien by the Department of Homeland Security that is listed on the front of Permanent Resident Cards,” and its employer handbook (the M-274) describes the field on the green card as one thing: “USCIS number/A-Number.” The current Form I-9 instructions write it the same way: “USCIS Number/A-Number (7 to 9 digits).” Same number, two labels; the card version just drops the “A” prefix.

So when a form asks for your A-number and your only document is a card with a “USCIS#” line, read the digits off the card and add the “A” in front.

Where to Find Your A-Number, Document by Document

Green card (Form I-551)

Front of the card, labeled “USCIS#,” on every card issued after May 10, 2010. It also appears in the machine-readable data on the back.

Work permit (EAD, Form I-766)

Front of the card, labeled “USCIS#.” This includes the OPT work permits issued to F-1 students.

Immigrant visa in your passport

If you immigrated through a U.S. consulate, the visa page (the “foil”) shows your A-number as the “Registration Number.” USCIS’s own tip for this one: if the number has fewer than 9 digits, pad it with a zero right after the “A,” so A12345678 becomes A012345678.

Immigrant data summary and USCIS Immigrant Fee handout

Consular immigrants get both at the visa interview; the A-number sits at the top of the data summary and the top right corner of the fee handout.

Receipt and approval notices (Form I-797)

Most notices show the A-number in the header block next to “USCIS#,” though not every I-797 variant includes it.

Any letter from DHS or USCIS

Per the I-765 instructions, the A-number appears on correspondence from the agency. If you have ever received a USCIS notice, check its header before hunting anywhere else.

I’m an F-1 Student. Do I Have an A-Number?

This is the single most-asked version of the question, and the answer depends on one document. If you have (or ever had) an OPT work permit, you have an A-number: every EAD carries a USCIS#, and that number is your A-number without the “A.” Pull out the card and read it off the front.

If you are an F-1 student who never applied for OPT or any other USCIS benefit, you most likely do not have an A-number yet. That is a normal situation with a form-approved answer: the marriage green card forms ask for the A-number “(if any),” and their instructions say to type or print “N/A” if you do not have one. The I-131 travel document instructions add the reassuring part: “If you do not have an A-Number, type or print ‘N/A.’ USCIS will assign one to you.” Filing the green card application is exactly how people get their first A-number, and it then shows up on the receipt notices USCIS mails back.

One edge case worth knowing about: some people end up with more than one A-number in the system, for example a number tied to an old student work permit and another assigned during a later case. USCIS consolidates records, but if your documents show two different numbers, treat that as something to disclose and resolve rather than silently picking your favorite; the forms ask about “any” A-numbers for a reason, and the interview is a natural place to flag it.

A-Number vs. Every Other Number USCIS Gives You

Immigration paperwork hands a couple four or five different identifiers, and forms ask for each by name. Here is the full lineup, in one place:

USCIS and related identifiers compared
Number	What it looks like	What it identifies, and where it lives
A-number	"A" + 7 to 9 digits	You, permanently. Cards ("USCIS#"), visa foil ("Registration Number"), USCIS letters
USCIS# on a card	9 digits, no "A"	Same as the A-number. Front of green cards and EADs
Receipt number	3 letters + 10 digits (IOE, MSC, EAC, WAC, LIN, SRC, NBC)	One application or petition. Top of Form I-797 notices
I-94 admission number	11 digits	One admission into the U.S.. The I-94 arrival record at i94.cbp.dhs.gov
Card number	Printed as "Card#"	The physical card itself. On the EAD front and the green card
Online Account Number (OAN)	Numeric account ID	Your online filing account. Online account profile, or the Account Access Notice
Social Security number	9 digits	Your tax and benefits record with SSA. Social Security card; issued by SSA, not DHS

A-number

What it looks like: "A" + 7 to 9 digits
What it identifies, and where it lives: You, permanently. Cards ("USCIS#"), visa foil ("Registration Number"), USCIS letters

USCIS# on a card

What it looks like: 9 digits, no "A"
What it identifies, and where it lives: Same as the A-number. Front of green cards and EADs

Receipt number

What it looks like: 3 letters + 10 digits (IOE, MSC, EAC, WAC, LIN, SRC, NBC)
What it identifies, and where it lives: One application or petition. Top of Form I-797 notices

I-94 admission number

What it looks like: 11 digits
What it identifies, and where it lives: One admission into the U.S.. The I-94 arrival record at i94.cbp.dhs.gov

Card number

What it looks like: Printed as "Card#"
What it identifies, and where it lives: The physical card itself. On the EAD front and the green card

Online Account Number (OAN)

What it looks like: Numeric account ID
What it identifies, and where it lives: Your online filing account. Online account profile, or the Account Access Notice

Social Security number

What it looks like: 9 digits
What it identifies, and where it lives: Your tax and benefits record with SSA. Social Security card; issued by SSA, not DHS

Two of these get confused constantly. The receipt number identifies a case, not a person: file three forms and you get three receipt numbers, all tied to the one A-number. And the online account number is its own thing entirely; the form instructions for the I-130, I-485, and I-765 all state it verbatim: “The OAN is not the same as an A-Number.” You only have an OAN at all if you previously filed something that produced a receipt number starting with IOE.

Format Quirks That Cause Rejections and Typos

The A-number’s variable length (7, 8, or 9 digits) meets forms and systems that want exactly 9. USCIS’s own guidance for its immigrant fee system says to pad short numbers with a zero after the “A” (A12345678 becomes A012345678). Paper forms print a 9-box grid for the digits after the “A-”; writing an 8-digit number left-aligned versus zero-padded is the kind of trivial mismatch that creates two “different” numbers in someone’s paperwork. When you copy the number, copy every digit, keep any leading zero, and use the same version everywhere in the packet.

The other quirk is the missing prefix on cards. If a form asks for the A-number and you copy the USCIS# straight off a card, you have the right digits; the “A” belongs in front, and the form’s printed “A-” before the boxes usually supplies it for you.

Can’t Find Your A-Number Anywhere?

Work through the documents in this order: any card USCIS has issued you (USCIS# on the front), the header of any USCIS notice or letter, the visa foil in your passport if you immigrated through a consulate, and the profile page of a USCIS online account if you have one. If none of those exist, the likeliest answer is that you do not have an A-number yet, which is exactly what the “(if any)” on the forms anticipates.

For someone who believes a number exists but cannot locate it (old case, lost paperwork), USCIS’s records request system (its FOIA process, at first.uscis.gov) can produce your immigration file, including the A-number. That takes time, so it is the last resort, not the first step.

And a timing note for marriage-based filers: if the green card packet is your first USCIS filing, the A-number assigned to you shows up on the receipt notices (Form I-797C) that arrive in the weeks after filing. Nothing needs chasing; it comes to you.

Frequently asked questions

What does an A-number look like?

The letter "A" followed by 7, 8, or 9 digits, such as A12345678 or A012345678. USCIS's glossary defines it as a unique seven-, eight-, or nine-digit number assigned by the Department of Homeland Security. On cards the "A" is dropped and the digits appear as the "USCIS#."

Is the USCIS number the same as the A-number?

On green cards and work permits, yes. USCIS's employer handbook labels the card field "USCIS number/A-Number," and the Form I-9 instructions treat "USCIS Number/A-Number (7 to 9 digits)" as one identifier. The card just omits the "A" prefix.

Do F-1 students have an A-number?

Only if USCIS has issued them something. An F-1 student with an OPT work permit has one: the USCIS# on the EAD card is the A-number. An F-1 student who never applied for OPT or another USCIS benefit usually has none yet, and writes "N/A" where forms ask for it.

Where is the A-number on a green card?

On the front, labeled "USCIS#," for every card issued after May 10, 2010. The same number is encoded on the back of the card.

What's the difference between an A-number and a receipt number?

The A-number identifies a person and normally stays with you across filings (a small number of people end up with more than one on file, as covered above). A receipt number identifies one case: 13 characters, 3 letters plus 10 digits (like IOE1234567890), printed on the Form I-797 notice for that application. A married couple's green card packet produces several receipt numbers for the immigrant spouse's one A-number.

What do I write if I don't have an A-number?

"N/A." The marriage green card forms ask for the A-number "(if any)," and their instructions direct "N/A" when you don't have one. USCIS assigns an A-number in connection with the case, and it appears on the receipt notices you get after filing.

My A-number has 8 digits but the system wants 9. What do I do?

Add a zero right after the "A": USCIS's own guidance gives the example of A12345678 becoming A012345678. Keep the padded version consistent everywhere once you use it.

Key takeaways

✓
The A-number is your permanent DHS file number: "A" plus 7 to 9 digits, defined in USCIS's glossary.
✓
On green cards and EADs it is printed on the front as "USCIS#," the same number without the "A."
✓
An F-1 student with an OPT work permit already has an A-number; one without any USCIS-issued document usually does not, and writes "N/A."
✓
Receipt numbers (3 letters + 10 digits) track individual cases; the A-number tracks the person across all of them.
✓
The USCIS Online Account Number is a different number; the form instructions say so verbatim.
✓
Pad an 8-digit A-number with a zero after the "A" when a system requires 9 digits, and keep it consistent across the whole packet.

This article is for educational purposes only and is not legal advice. Green Card Genius is self-help immigration software, not a law firm, and does not provide legal representation. Information current as of July 2026.

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