USCIS A-Number in 2026: What It Is, Who Has One, and Where To Look First

USCIS A-Number in 2026: What It Is, Who Has One, and Where To Look First

Short answer: USCIS says an A-Number, also called an Alien Registration Number or Alien Number, is a unique seven-, eight-, or nine-digit number assigned by the Department of Homeland Security to a noncitizen. USCIS also says the USCIS Number on the front of permanent resident cards issued after May 10, 2010 is a unique nine-digit number assigned to an alien, and its glossary cross-references that number back to the A-Number definition. By contrast, USCIS says a receipt number is a separate 13-character case-tracking identifier for a specific application or petition. [1][2][3]

That distinction matters because many people search for an A-Number when they really have a receipt number, or they assume every immigration document uses the same identifier. If you are trying to complete a filing, respond to a government notice, or prepare for a consultation, it is safer to identify the number correctly than to guess.

If your question is really about whether you had to complete the recent alien-registration process, use our separate guide on the USCIS alien registration requirement. That topic is related, but it is not the same as locating or understanding an A-Number.

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USCIS defines the A-Number as a unique identifier assigned by DHS to a noncitizen. [1]

The practical takeaway is simple: the A-Number is an identity number tied to the person, not a tracking number tied to only one filing.

That is why the same person may see the same A-Number appear across different parts of an immigration history, while receipt numbers change from case to case.

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Sometimes, yes.

USCIS says the USCIS Number is a unique nine-digit number listed on the front of permanent resident cards (Form I-551 or Green Card) issued after May 10, 2010. USCIS also tells readers to see the Alien Registration Number or Alien Number entry. [2]

So for many green card holders, the number labeled USCIS Number on the card is the same identifier people mean when they ask for the A-Number.

That does not mean every immigration number on every document is interchangeable. The safest approach is to use the exact label the form or notice gives you and confirm whether the document is referring to an A-Number, a USCIS Number, or something else entirely.

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No.

USCIS says a receipt number is a unique 13-character identifier for each application or petition it receives. USCIS also says the receipt number has 3 letters followed by 10 numbers, and that you can find it on USCIS notices of action. [3]

That means:

• an A-Number identifies the person,
• while a receipt number identifies a particular filing.

If a form asks for an A-Number and you type a receipt number instead, you may create an avoidable mismatch in the filing.

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Not everyone encounters an A-Number in the same way, and not everyone searching for one will necessarily have an easy document match in front of them.

USCIS's current Alien Registration Requirement guidance is useful here because it lists many categories of people who are already registered in DHS systems. USCIS says this group includes, among others: [4]

• lawful permanent residents,
• people paroled into the United States,
• nonimmigrants issued Form I-94, I-94A, or I-94W,
• people issued an employment authorization document,
• and people who filed certain adjustment applications and provided fingerprints.

That does not mean every person in those categories will instantly know where the number appears on a specific document. It does mean many noncitizens already have DHS records even when they are uncertain which number a form is asking for.

USCIS also says some people are not registered, including certain people who entered without inspection and certain Canadian visitors who were not issued registration evidence and have not otherwise registered. [4]

So if you cannot clearly identify an A-Number from your own records, do not assume one exists in the way you expect. In some cases the safer move is to review the exact filing history and supporting documents before filling in the field.

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The first place to look depends on your immigration history.

If you are a green card holder

USCIS says the USCIS Number is listed on the front of permanent resident cards issued after May 10, 2010, and its glossary points readers from that term back to the Alien Registration Number definition. [1][2]

For many permanent residents, that is the quickest place to check first.

If you are working from a USCIS notice or filing packet

Use the exact wording on the document. If the notice or form separately labels an A-Number or Alien Registration Number, rely on that field rather than assuming a different identifier is interchangeable.

If all you can find is a receipt number

USCIS says receipt numbers are 13-character case identifiers shown on notices of action. [3] That number may help you track a case, but it is not the same thing as an A-Number.

If you still cannot find the number

Do not invent one. A case-specific review is safer than guessing, especially if the form is important, time-sensitive, or tied to identity matching.

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The most common problems are avoidable:

1. Using a receipt number where the form asks for an A-Number.
2. Assuming the alien-registration issue and the A-Number issue are the same question. They overlap, but they are not identical.
3. Guessing when the record is unclear. A bad number can create mismatched identity records.
4. Assuming every noncitizen has the same kind of DHS identifier available on demand. Immigration history matters.
5. Relying on generic internet advice instead of the actual document label.

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Legal review is often useful when:

• a filing is being rejected or delayed because of identity-number confusion,
• the person has multiple prior filings and cannot tell which number belongs where,
• the record includes immigration court, parole, adjustment, or consular history,
• or the person is trying to correct a filing that already used the wrong identifier.

The legal issue is often not the number itself. The real issue is whether the filing record, the person's status history, and the government's identity record all match.

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Does everyone dealing with USCIS already have an A-Number?

No. Some people clearly do, and some do not. USCIS's registration guidance itself distinguishes between people who are already registered and people who are not. [4]

Is the A-Number the same as the USCIS Number on a green card?

For many permanent residents, yes. USCIS says the USCIS Number on the front of permanent resident cards issued after May 10, 2010 is a unique nine-digit number assigned to an alien, and USCIS cross-references that term to the A-Number definition. [1][2]

Is the A-Number the same as a receipt number?

No. USCIS says the receipt number is a separate 13-character identifier for a particular application or petition. [3]

What if I have a receipt notice but cannot find an A-Number anywhere?

That can happen. The safe response is not to guess. Review the exact record you have and, if needed, get case-specific guidance before submitting a number that may belong to a different filing category.

Does an A-Number by itself prove lawful status?

No. The number is an identifier. It is not a standalone grant of immigration status, work authorization, or a legal benefit.

Is this the same topic as the 2025-2026 alien registration requirement?

No. That requirement is about who must register or re-register and what evidence of registration may be required. This page is about identifying and understanding the A-Number itself. For that separate issue, see our alien registration requirement guide.

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The information here is general and educational. If a USCIS, NVC, or consular filing asks for an A-Number and your record is unclear, using the wrong identifier can create avoidable delays.

If you need help reviewing the right number for a pending case, a targeted legal review can help you correct the record before a small clerical issue becomes a larger filing problem.

Notes

[1] U.S. Citizenship and Immigration Services, A-Number/Alien Registration Number/Alien Number (A-Number or A#), accessed October 2, 2026.

[2] U.S. Citizenship and Immigration Services, USCIS Number, accessed October 2, 2026.

[3] U.S. Citizenship and Immigration Services, Receipt Number, accessed October 2, 2026.

[4] U.S. Citizenship and Immigration Services, Alien Registration Requirement, accessed October 2, 2026.