Do U.S. Citizens Have an Alien Registration Number?

Some U.S. citizens have an Alien Registration Number because they received one before becoming citizens. Naturalization does not make that historical identifier disappear. Someone who has always been a citizen generally does not need an A-number merely to prove citizenship or complete a form that applies to noncitizens. [1]

Rules that determine the answer

The A-number, also called the USCIS number, identifies an immigration record. It is different from a Social Security number, USCIS online-account number, application receipt number, and naturalization-certificate number. SAVE guidance lists these as distinct identifiers. A form asking for a certificate number should not be answered with the A-number simply because both appear on the same document. [2]

CMS guidance expressly recognizes that naturalized and derived citizens can provide identifying information from their citizenship documents, including an alien number. The number’s continued appearance is therefore compatible with citizenship. [1] An agency’s request for an immigration identifier also should not be mistaken for a demand to obtain new immigration status. If the application instead asks whether the person is a U.S. citizen, answer that status question accurately. A U.S. passport or appropriate citizenship certificate serves a different evidentiary purpose from the identifier used to locate a former immigration file. [2]

What to do next

  1. Check the exact field label and instructions before entering a number.
  2. A naturalized citizen can look for a USCIS number on citizenship documents or an older immigration record; keep it separate from the certificate number.
  3. If no A-number was ever assigned, use the form’s permitted “not applicable” response rather than inventing one.
  4. If documents show conflicting identifiers, ask the receiving agency which record it needs and use an authorized correction or records-request process.

Practical example

A naturalized citizen applying for Marketplace coverage sees fields for a Naturalization Certificate number and a USCIS number. Those are separate entries. Providing the correct A-number does not mean the person is still a noncitizen.

For related situations, see A-numbers for H-4 visa holders and removing a Social Security card work restriction.

Primary sources

  1. CMS: Citizenship verification for naturalized and derived citizens
  2. USCIS SAVE: Immigration identifiers and enumerators

Sources checked: October 31, 2026.