An Alien Number and a Green Card number are not the same thing, even though both appear on the same card. Your Alien Number (also called an A-Number) is a personal identifier that follows you through every stage of the immigration system. “Green Card number,” in everyday use, usually means the serial number printed on the back of the physical card, and that one changes every time USCIS issues you a new card. The distinction between an alien number vs a green card number matters because employers, forms, and government agencies each ask for a specific one, and entering the wrong number can hold up your case or your paycheck.
What the Alien Number Is
An A-Number is a seven-, eight-, or nine-digit number that the Department of Homeland Security assigns to a noncitizen.1U.S. Citizenship and Immigration Services. A-Number/Alien Registration Number/Alien Number It attaches to every petition, application, and decision tied to you. File Form I-485, and the approval notice carries your A-Number. Enter on an immigrant visa, and it appears on the visa stamp in your passport.
The number does not change when your status changes. Someone who moves from an employment authorization document to lawful permanent residence and then to naturalized citizenship keeps the same A-Number the entire time. USCIS uses it to pull up your whole immigration history in one place.
You may also see it labeled “USCIS Number.” On Permanent Resident Cards issued after May 10, 2010, USCIS prints a nine-digit version on the front of the card under “USCIS#.”2U.S. Citizenship and Immigration Services. USCIS Number If your A-Number has fewer than nine digits, USCIS adds leading zeros. A-Number A1234567 becomes USCIS# 012345678 on the card.
What People Actually Mean by “Green Card Number”
The confusion exists because three separate numbers appear on or in connection with a Permanent Resident Card (Form I-551). People use “Green Card number” to mean different ones depending on context.
- Alien Number (A-Number): Your personal identifier within the immigration system. It appears on the front of the card under “USCIS#” and again in the machine-readable zone on the back. It stays with you permanently.
- Card or Document Number: A serial number unique to the physical card in your hand. It consists of three letters followed by ten digits and is printed on the back of the card. When someone casually says “Green Card number,” this is usually the one they mean.3U.S. Citizenship and Immigration Services. List A Documents That Establish Identity and Employment Authorization
- Receipt Number: A 13-character code (three letters followed by ten digits) that USCIS assigns to track a specific application. The first three letters indicate the service center. You find it on Form I-797 notices, not on the card.4U.S. Citizenship and Immigration Services. Receipt Number
The Card/Document Number and the Receipt Number look similar in format, but they do different jobs. The Card/Document Number identifies one specific piece of plastic. The Receipt Number tracks one specific application through USCIS. Neither one is your A-Number.
Where to Find Each Number
On the Green Card
Look at the front of the card first. Your A-Number appears near the top, labeled “USCIS#,” as a nine-digit number with leading zeros if needed.2U.S. Citizenship and Immigration Services. USCIS Number The same number is embedded in the machine-readable zone on the back.
The Card/Document Number is on the back, typically at the top. Three letters, then ten digits. This is the number that changes when you get a new card.
On Other Immigration Documents
Your A-Number shows up on more than just the green card:
- Employment Authorization Document (Form I-766), listed under “USCIS#” on the front.
- Immigrant visa stamp in your passport, labeled “Registration Number.” If it has fewer than nine digits, add a zero after the “A” to make it nine.5U.S. Citizenship and Immigration Services. Immigrant Fee Payment: Tips on Finding Your A-Number and DOS Case ID
- Immigrant Data Summary, the sheet stapled to the front of the immigrant visa package from the U.S. embassy. Your A-Number appears at the top.5U.S. Citizenship and Immigration Services. Immigrant Fee Payment: Tips on Finding Your A-Number and DOS Case ID
- USCIS notices (Form I-797). Both the A-Number and the Receipt Number appear near the top.6U.S. Citizenship and Immigration Services. Form I-797 Types and Functions
- Asylum grant letters and immigration court documents.
The Receipt Number is what you enter into the USCIS Case Status Online tool. Type the 13-character code without dashes to see where your application stands.
What Changes When You Renew or Replace the Card
A standard green card is valid for ten years. A conditional card, issued to people who obtained residence through a recent marriage, is valid for two years.7U.S. Citizenship and Immigration Services. Conditional Permanent Residence When you receive a replacement card, your A-Number stays exactly the same. The Card/Document Number will be different, because it belongs to the new piece of plastic, not to you.
This is where people get tripped up. If a form or employer asks for your “Green Card number” and you copy it off an expired card, the Card/Document Number will not match your current card. Your A-Number, by contrast, matches every immigration document you have ever received. When you are unsure which number a form wants, read the field label. “USCIS Number” or “A-Number” means your personal identifier. “Card Number” or “Document Number” means the serial number from the card you are presenting.
Which Number a Form or Employer Is Asking For
Form I-9 Employment Verification
Every employer must complete Form I-9 for each new hire. If you check “lawful permanent resident” in Section 1, the form asks for your seven- to nine-digit A-Number.8U.S. Citizenship and Immigration Services. Instructions for Form I-9, Employment Eligibility Verification If you present the green card as a List A document in Section 2, the employer records the Card/Document Number from the back. Mixing them up causes a mismatch that can delay your start date.
Social Security Card Applications
To apply for an original Social Security Number or a replacement card, a noncitizen must show proof of immigration status. For a lawful permanent resident, that means presenting the green card.9Social Security Administration. Learn What Documents You Will Need to Get a Social Security Card SSA uses the information on the card, including the A-Number, to verify status with DHS.
USCIS Online Account
Creating a USCIS online account requires an email address and two-step verification, not an A-Number. Once the account exists, adding a paper-filed case to it requires the Receipt Number.10U.S. Citizenship and Immigration Services. How to Create a USCIS Online Account The A-Number becomes relevant when you call the USCIS Contact Center or attend an appointment, where staff use it to pull your file.
If You Have Lost Your Alien Number
Check every immigration document you can find first. Old I-797 notices, expired EADs, and visa stamps in previous passports all carry the same A-Number.
If none of those are available, the fastest option is calling the USCIS Contact Center at 1-800-375-5283. A representative can look up your A-Number using your name, date of birth, and other identifying details. You can also schedule an in-person appointment at a USCIS field office.
The formal option is a Freedom of Information Act request, filed on Form G-639 with the USCIS National Records Center. The request needs your full name, current address, date and place of birth, and a signature that is either notarized or submitted under penalty of perjury.11U.S. Citizenship and Immigration Services. Instructions for Form G-639, Freedom of Information/Privacy Act Request Do not send payment with the initial request; USCIS will contact you about any fees. A FOIA request takes longer than a phone call but produces an official record of your immigration history.