What Is an Alien Registration Number (A-Number)?

An Alien Registration Number, usually called an A-Number, is the unique identifier the Department of Homeland Security assigns to noncitizens to track their immigration records for life. It consists of seven, eight, or nine digits preceded by the letter “A,” and you can find it on your green card, Employment Authorization Document, immigrant visa stamp, Certificate of Naturalization, or any official USCIS notice.¹ On documents issued in recent years, the same number is labeled “USCIS Number.” It is the same identifier.²

What the Number Is and Who Receives One

Your A-Number is a permanent personal identifier used only for immigration matters. It is not the same as a Social Security Number, which handles taxes and employment benefits. DHS assigns the A-Number once and never changes it, even when your status does. You keep the same number when you move from a work visa to a green card, and you keep it after you naturalize.

Because the number stays with you, every application you file, every decision made on your case, and every enforcement action goes into a single file under that number. If your A-Number has fewer than nine digits, USCIS treats it as a nine-digit number by adding a zero after the “A.” So “A12345678” is entered on forms as “A012345678.”³

Not every foreign national in the country receives an A-Number. The government assigns one when it opens a formal immigration file for you, typically when you take a step toward longer-term status: applying for a green card, seeking asylum or refugee status, applying for certain work authorization (including Optional Practical Training for students), or being placed in removal proceedings. Short-term visitors on tourist or business visas generally do not get an A-Number; their entries are tracked through the I-94 arrival/departure record.

Where to Find Your A-Number

The label and placement vary from one document to another, but the number itself is always the same.

Permanent Resident Card

On a green card (Form I-551), the A-Number appears on the front. Cards issued after May 2010 label it “USCIS Number” or “USCIS#/A-Number” and repeat it on the back. Older cards may call it the “A-Number” or “Registration Number.”⁴

Employment Authorization Document

On an EAD (Form I-766), the number is printed on the front, labeled “USCIS Number.” The card design that took effect on January 30, 2023 rearranged some fields, but the A-Number is still prominently shown.⁴

Immigrant Visa Stamp

If you entered on an immigrant visa, the A-Number is printed on the visa foil inside your passport, labeled “Registration Number.”³ Add a zero after the “A” if the printed number has fewer than nine digits when you enter it on a USCIS form.

Certificate of Naturalization

Even after you become a U.S. citizen, the number stays on your Certificate of Naturalization (Form N-550), where it is labeled “USCIS Registration No.”⁵ You may need it when you apply for a U.S. passport or petition for family members.

USCIS Notices and Court Documents

Form I-797 (Notice of Action), which confirms receipt of an application or communicates a decision, displays the A-Number near the top of the page next to your name and receipt number.⁴ If you have been in immigration court, your A-Number also appears on all correspondence from the Executive Office for Immigration Review.⁶

Include the Number on Every Immigration Form

You have to include your A-Number on nearly every immigration form you file after it has been assigned. Leaving it off can delay processing or cause the form to be returned. When a form asks for a “USCIS Number” and another form asks for an “A-Number,” enter the same number in both places.

How to Recover a Lost A-Number

If you cannot locate your A-Number on any document, you have three practical options.

Check older paperwork. The number appears on most official notices USCIS has ever sent you, including approval letters and receipt notices.
Call the USCIS Contact Center at 800-375-5283 (TTY 800-767-1833), open Monday through Friday, 8 a.m. to 8 p.m. Eastern. Have your full name, date of birth, and any receipt numbers ready to verify your identity.
File a FOIA request using Form G-639 (Freedom of Information/Privacy Act Request) to obtain a copy of your immigration records. If you do not know your A-Number, leave that field blank; the form’s instructions account for this. You can also submit the request online at uscis.gov/foia.⁷

Keeping Your A-Number Private

USCIS classifies the A-Number as personally identifiable information because it can be used, alone or with other details, to identify you specifically.⁸ Treat it with the same care you give a Social Security Number. Share it only on official government forms, in verified contact with USCIS, or with an attorney you have authorized to represent you.

If a third party such as an employer’s immigration attorney or an accredited representative needs to make inquiries for you, USCIS requires a written, signed, and notarized privacy release before it will discuss case-specific information with that person.⁸ Be careful about sending the number by email or handing it to anyone you have not specifically authorized. Unauthorized use of immigration identifiers can enable identity fraud.

1
U.S. Citizenship and Immigration Services. A-Number/Alien Registration Number/Alien Number (A-Number or A#)
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U.S. Citizenship and Immigration Services. USCIS Number
3
U.S. Citizenship and Immigration Services. Immigrant Fee Payment: Tips on Finding Your A-Number and DOS Case ID
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U.S. Citizenship and Immigration Services. 13.1 List A Documents That Establish Identity and Employment Authorization
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U.S. Citizenship and Immigration Services. Chapter 3 – Certificate of Naturalization
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Executive Office for Immigration Review. Customer Service Initiatives
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U.S. Citizenship and Immigration Services. Form G-639, Freedom of Information/Privacy Act Request
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U.S. Citizenship and Immigration Services. Chapter 7 – Privacy and Confidentiality