Your green card number—also called your "card number," "document number," or "receipt number"—is a 13-character alphanumeric code that USCIS assigns to each physical Permanent Resident Card it issues. It identifies that specific card document, not you as a person.

Because it identifies the card rather than the individual, your green card number changes every time USCIS issues you a new card—after renewal, replacement, or a status adjustment. Your A-Number (Alien Registration Number) is the opposite: it's assigned once and never changes.

Here's how the three main identifiers on your card compare:

On cards issued after May 2010—including the current 2023-redesigned card—your green card number is printed only in the machine-readable zone on the back of the card, never on the front. The MRZ is the three lines of letters, numbers, and "less than" symbols (<) that run across the bottom.

Specifically: the first line is 30 characters long and breaks down as: a 2-character residency status code, the 3-letter issuing country code (USA), your 9-digit A-Number, a 1-digit check digit, and then a 15-character field (characters 16–30) that holds your 13-character green card number followed by "<<" filler. To pull out the number, strip the trailing "<" filler first—then take what's left of that final field. Doing it in the other order (counting backward from the end of the line before removing the filler) will cut off the first two characters of your actual number and hand you the wrong code.

A green card number looks like this: SRC0000000110 or NBC2004551423 or in this example it's: MSC0000000110

The field on the front of your card labeled "USCIS#" is your Alien Registration Number (A-Number)—not your green card number. It appears in 9-digit format (e.g., 123-456-789) and is your permanent identifier with the Department of Homeland Security. According to USCIS, the A-Number is assigned once and follows you throughout your entire immigration history—it never changes, no matter how many cards you receive.

The "USCIS#" label causes confusion because it sounds like it should be the green card number. It isn't.

On the back of the card (machine-readable zone):

The "less than" symbols (<<) are placeholders that fill unused character spaces.

The 13-character code isn't random—it encodes information about how and where your application was processed. Here's how it breaks down:

If your code says "SRC" or "LIN," your card was processed by what is now called the Texas Service Center and Nebraska Service Center respectively—USCIS has renamed several centers over the years, so older codes are still valid.

This is where most confusion happens, because different forms call for different numbers.

Here's the quick guide:

Form I-90: When filing for renewal or replacement, the "USCIS Card Number" field calls for the 13-character green card number from the back of your card. ("Document number," "card number," and "permanent resident card number" all refer to this same 13-character code.)

Form I-9: When your employer uses your green card (I-551) as a List A document, USCIS instructions direct them to enter the USCIS Number from the front of the card—your A-Number. This catches many people off guard: the I-9 "Document Number" field for a green card calls for the A-Number, not the 13-character code. If your employer has questions, USCIS I-9 Central is the authoritative source.

Form N-400: When applying for naturalization, you'll provide both your A-Number and your current green card number.

Green card numbers are assigned under federal law and work identically regardless of which state you live in. USCIS issues your card centrally, and the numbers on it—your green card number and your A-Number—are recognized by federal agencies nationwide.

State agencies may have their own requirements. Some states ask you to present your physical card when applying for a driver's license or state ID, rather than just providing the number. For all federal immigration forms, the number on your card is what you need. If you're unsure what a state agency requires, contact that agency directly or check with your immigration attorney.

Immigration paperwork is designed to be precise, and small errors—using the wrong number on a form, or mixing up your A-Number and green card number—can delay processing or trigger a Request for Evidence (RFE).

An immigration attorney with Marble can review your documents to confirm you're using the correct identifiers on each form, help you file Form I-90 if your card is lost, damaged, or contains an error, and guide you through the naturalization process when you're ready to apply for U.S. citizenship.

Most errors on immigration forms aren't caused by not knowing the law—they're caused by mixing up two numbers that look similar and carry similar-sounding names. The green card number lives in the machine-readable zone on the back; the "USCIS#" on the front is your A-Number. Getting that distinction right puts you ahead of most people filling out these forms.

Disclaimer: This article is for general informational purposes only and does not constitute legal advice. Laws vary by state. For guidance specific to your situation, speak with a licensed family law attorney.