An A-Number (Alien Registration Number) is a unique seven-, eight-, or nine-digit number that the Department of Homeland Security assigns to a noncitizen. It is a different identifier from the USCIS Number, from the USCIS Online Account Number, and from the 13-character receipt number printed on case notices. Mixing them up is a common cause of rejected or delayed requests.
Quick answer
| Number | What it identifies | Format per USCIS |
|---|---|---|
| A-Number | The person | Seven, eight, or nine digits |
| USCIS Number | The person (a related term in the glossary) | Nine digits; listed on the front of Permanent Resident Cards issued after May 10, 2010 |
| USCIS Online Account Number | The online account used for filing | Unique number; one account for all cases |
| Receipt Number | One application or petition | 13 characters: three letters, then ten digits |
Why several numbers exist
Each number answers a different question. One answers who the person is in DHS records. Another answers which online account is used to file. A third answers which single application or petition USCIS received. A fourth is printed on newer cards. Forms and notices ask for a specific one, so the label next to the blank matters more than how a number looks.
A-Number
The USCIS glossary defines the A-Number, also called the Alien Registration Number or Alien Number (written A-Number or A#), as a unique seven-, eight-, or nine-digit number that DHS assigned to a noncitizen. It stays with the person across applications, which is why forms ask for it whenever the person already has one. The glossary points readers to the “USCIS Number” entry as a related term.
USCIS Number
The glossary defines the USCIS Number as a unique, nine-digit number that DHS assigned to a noncitizen. The same entry says it is listed on the front of Permanent Resident Cards (Form I-551, also called a Green Card) issued after May 10, 2010. The glossary does not say that the USCIS Number and the A-Number are always identical, so the exact field label on a card or form should be followed. Anyone unsure which one a form wants can check the form instructions or ask USCIS.
USCIS Online Account Number
The glossary describes the USCIS Online Account Number as a unique identification number issued by the USCIS online filing system account. USCIS states that a person should have one account number for all cases submitted. It identifies the online account, not the person’s immigration record and not an individual case.
Receipt Number
The glossary says the receipt number is a unique 13-character identifier that USCIS provides for each application or petition it receives. It has three letters followed by ten numbers, and it appears on USCIS notices. The letters, such as EAC, WAC, or LIN, are examples of the three-letter prefix. A new application receives a new receipt number, even for the same person.
Where each number tends to appear
- A-Number: on documents USCIS has issued to the person; check the document itself or earlier USCIS notices.
- USCIS Number: on the front of a Permanent Resident Card issued after May 10, 2010.
- Online Account Number: in the person’s own USCIS online account.
- Receipt Number: on the receipt notice for the specific case.
If a number cannot be found on any document, USCIS is the authority to ask. Guessing or reusing a number from another case can attach a form to the wrong record.
Which number is used for what
The USCIS page on replacing a Green Card gives a concrete example. A person who wants to ask about a Form I-90 filing is told to have a name, date of birth, receipt number, and A-Number ready when calling the USCIS Contact Center. In that situation the receipt number points to the one case, and the A-Number points to the person. The page also says to wait 72 hours after filing before checking the case online. Because the receipt number belongs to one case only, it cannot stand in for the A-Number on a later form.
Common mistakes
- Entering a receipt number where a form asks for an A-Number.
- Opening a second online account instead of using the existing one.
- Assuming an old receipt number can be used for a new application.
- Dropping a digit: A-Numbers can have fewer than nine digits, and the form’s instructions explain how to enter them.
- Treating the online account number as proof of status. It only identifies the account.
Checklist before filling in any number
- Read the exact label beside the field.
- Copy the number from a USCIS document, not from memory.
- Count the characters: a receipt number has 13, and an A-Number has seven to nine digits.
- Match the number to the right document: a receipt notice for the case, the card or an earlier notice for the person.
- Keep a copy of every receipt notice, since each new case gets its own number.
Frequently asked questions
Is the A-Number the same as the number on the Green Card?
They are defined as different identifiers in the glossary. The Green Card is evidence of status, and the A-Number identifies the person in DHS records. The glossary says the USCIS Number is listed on the front of cards issued after May 10, 2010. Read the exact fields on the card or consult USCIS for how each one is labeled.
How many digits does an A-Number have?
USCIS says seven, eight, or nine digits.
What does a receipt number look like?
Three letters followed by ten numbers, 13 characters in total.
Can one person have more than one USCIS online account?
USCIS states that a person should have one account number for all cases, so a single account is the intended setup.
Does a new application get a new receipt number?
Yes. USCIS provides a receipt number for each application or petition it receives.
Related reading
- Is “green card” capitalized? Style and official usage
- Green Card expiration dates and renewal
- Green Card FAQ
- DV lottery requirements
About this guide
This website is for information only. It is not affiliated with the U.S. government, does not give legal advice or consultations, and does not offer application services. The current official instructions control, because rules change each year.
Last verified: October 2026. Sources: USCIS glossary; USCIS page on replacing a Green Card.