Alien Number (A-Number): What It Is and Where to Find It

An Alien Registration Number, usually called an A-Number, is a unique seven-, eight-, or nine-digit identifier that the Department of Homeland Security assigns to a noncitizen and keeps on file for life.¹ It follows you from your first immigration application through naturalization, and it never changes or expires. If you have a green card, a work permit, or an immigrant visa, you already have one.

What the Number Looks Like

An A-Number is a digit sequence preceded by the letter “A.” USCIS has issued them in seven-, eight-, and nine-digit lengths over the years, but the agency standardizes everything to nine digits in its databases by padding shorter numbers with leading zeros.¹ An older number written as A1234567 shows up in current records as A001234567. The digits themselves do not encode any geographic or category information; they are assigned in sequence.

On documents issued after May 10, 2010, especially Permanent Resident Cards, the same number is labeled “USCIS Number” or “USCIS#” rather than “Alien Registration Number.”² It is the same number. If a form asks for a USCIS Number and you only know your A-Number, enter the same digits.

Where to Find Your A-Number

Your A-Number is printed on almost every immigration document you have received. Check these first.

Green Card (Form I-551)

On green cards issued after May 2010, the number appears on the front under “USCIS#.” Older cards may label the same field “Alien Registration Number” or “A#.”²

Employment Authorization Document (Form I-766)

Work permits follow the same layout as the green card, with the A-Number on the front under “USCIS#.”³

Immigrant Visa Stamp

If you entered the U.S. on an immigrant visa, look at the visa foil in your passport. The A-Number is printed there as the “Registration Number.”⁴

Notice of Action (Form I-797) and Immigrant Data Summary

Every I-797 notice from USCIS carries your A-Number in the personal information section near the top of the page. The Immigrant Data Summary included in a visa packet also prints it at the top.⁴ Even expired notices still show a valid A-Number.

Form I-94 Lookup

The CBP I-94 portal accepts the A-Number as a lookup field, which helps if you have lost other documents and need to pull up your travel history.⁵

If You Cannot Find It

Misplacing your A-Number is common and does not affect your status. Work through these options in order:

Dig out old paperwork. Approval notices, prior work permits, expired green cards, visa stamps, and any I-797 you have ever received will show the number.
Log into your myUSCIS account. If you have filed a form online, the A-Number often appears in your case history or profile.
Call the USCIS Contact Center at 800-375-5283 (TTY 800-767-1833). An agent can look up your number using your name and date of birth.⁶
File a FOIA request for your own immigration records through the USCIS FIRST portal online, or by mailing Form G-639. The online portal returns records faster and digitally; the paper form is answered by mail.⁷

If you are filling out a USCIS form and have never been assigned an A-Number, write “N/A” or leave the field blank. The Form I-485 instructions, for example, ask for the A-Number “if any,” meaning the field is optional for first-time applicants.⁸

Do Not Confuse It With These Other Numbers

Several federal identifiers look similar. Entering the wrong one on a form can delay your case or trigger a rejection.

Social Security Number

An SSN is issued by the Social Security Administration for tax reporting, employment, and federal benefits. Many noncitizens hold both an SSN and an A-Number, but they are unrelated. Your SSN is tied to earnings and tax records; your A-Number is tied to your immigration file. Never enter an SSN where a form asks for an A-Number.

ITIN

An Individual Taxpayer Identification Number is a nine-digit IRS number for people who file taxes but are not eligible for an SSN. It always begins with 9 and is formatted like an SSN. It has no immigration function and does not grant status or work authorization. The A-Number is strictly an immigration identifier and has no tax function.

Receipt Number

A receipt number is a 13-character code, three letters followed by ten digits, that USCIS assigns to a specific application or petition.⁹ You may collect many receipt numbers over the years, one per filing. The A-Number is assigned to you as a person and stays the same across every filing. Online case status checks at egov.uscis.gov use a receipt number, not the A-Number.

USCIS Online Account Number

The Online Account Number (OAN) is a login credential for the myUSCIS portal. The I-485 instructions state directly that “the OAN is not the same as an A-Number.”⁸ It has no legal significance outside the portal.

Who Gets Assigned One

The government assigns an A-Number when a noncitizen has a significant interaction with the immigration system. The common triggers:

Approval of a green card application. The number appears on the Permanent Resident Card.²
Filing Form I-765 for a work permit, if you don’t already have one. The number then appears on the Employment Authorization Document.
Receiving an immigrant visa at a U.S. consulate abroad. The number is printed on the visa stamp as the Registration Number.⁴
Being placed in removal proceedings, so the immigration court can track your case.¹⁰
Admission as a refugee or grant of asylum, which links future benefit applications to your record.⁶

Not every immigration filing generates an A-Number. Nonimmigrant visa petitions and basic case status checks do not create one. The number is reserved for situations where the government needs to build a lasting record tied to a specific person.

The Number Is Permanent

Once assigned, your A-Number never changes. It stays the same as you move from one status to another, adjust to permanent residence, or naturalize. Every application, approval, denial, and court appearance is threaded through that single number.¹ Each A-Number corresponds to a physical or digital Alien File (A-File) holding the full history of your interactions with the immigration system: visa applications, photographs, correspondence, and more.¹¹ Naturalization records are folded into the same file, so the A-Number remains part of your record after you become a citizen and appears on the Certificate of Naturalization.

If an agency error or a name change ever produces a duplicate A-Number for you, contact USCIS to have the files merged. Duplicates can cause processing delays, background check flags, and conflicting records across agencies.

The A-Number is less sensitive than a Social Security Number, but it can still be used to look up case details, so share it only where an official form or agency requests it.

Registration Duties You May Not Know About

Being assigned an A-Number comes with a legal duty most people satisfy without noticing, because visa and green card applications include the required registration and fingerprinting. Two obligations do catch people off guard.

First, address changes must be reported within ten days. USCIS provides an online change-of-address tool for this. Failing to notify the government can result in up to 30 days in jail.¹²

Second, willfully failing to register or provide fingerprints is a federal offense carrying a fine and up to six months in prison. Submitting fraudulent registration information carries the same six-month penalty, and counterfeiting registration documents is a felony punishable by up to five years. Violating the registration rules is also a ground for deportation, with a defense available only if the failure was not willful or was reasonably excusable.¹²

1
U.S. Citizenship and Immigration Services. A-Number/Alien Registration Number/Alien Number
2
U.S. Citizenship and Immigration Services. USCIS Number
3
U.S. Citizenship and Immigration Services. 13.1 List A Documents That Establish Identity and Employment Authorization
4
U.S. Citizenship and Immigration Services. Immigrant Fee Payment: Tips on Finding Your A-Number and DOS Case ID
5
U.S. Customs and Border Protection. I-94/I-95 Website
6
U.S. Citizenship and Immigration Services. Immigration Benefits in EOIR Proceedings
7
U.S. Citizenship and Immigration Services. Freedom of Information/Privacy Act Request
8
U.S. Citizenship and Immigration Services. Form I-485 Instructions for Application to Register Permanent Residence
9
U.S. Citizenship and Immigration Services. Receipt Number
10
United States Department of Justice. EOIR Case Information
11
U.S. Citizenship and Immigration Services. A-Files Numbered Below 8 Million
12
Congress.gov. Alien Registration Requirements