Can you file by mail?
Answer
Yes, to your local USCIS office
Explanation
Yes, Form N-400 can be filed by mail to a USCIS Lockbox at the address specified in the most recent version of the form instructions, which are available at uscis.gov/n-400. USCIS does not accept paper N-400 applications at its field offices; all paper filings must be sent to one of the agency's centralized Lockbox facilities, which are operated by the U.S. Department of the Treasury through contracts with commercial banks. The correct Lockbox address depends on the applicant's state of residence; the current instructions list two principal addresses: a Phoenix Lockbox for some Western states and a Dallas Lockbox for most other states (filing addresses can change, so applicants should always verify the current address on the form instructions before mailing).
Applicants must mail the completed Form N-400, signed in ink, with two passport-style photographs (only required for applicants residing outside the United States), the filing fee of $760 (paper filing under the April 2024 fee schedule, payable by personal check, cashier's check, or money order made payable to U.S. Department of Homeland Security), and copies of supporting documents (front and back of the green card, marriage certificates, divorce decrees, tax transcripts, etc.). Originals are not sent with the application; originals are presented at the interview. USCIS recommends mailing the application by a trackable method (USPS Certified Mail with Return Receipt, FedEx, UPS, or DHL) and retaining a copy of the entire packet for the applicant's records.
After the Lockbox receives the application, USCIS issues a receipt notice (Form I-797C, Notice of Action) within two to four weeks, providing the receipt number, an estimated processing time, and confirmation that the application was accepted. From there, the case proceeds through biometrics, interview, and oath ceremony. Paper filing is somewhat slower than online filing on average (often by 30 to 60 days) because of the additional handling required, but the substantive rights and procedures are the same. Applicants who prefer paper filing because they lack reliable internet access, prefer to keep paper records, or are following the advice of a community legal organization can use this pathway without disadvantage.
Why this matters for your test
Mail filing is fully supported and remains a valid pathway for applicants who prefer it. Knowing that the application goes to a Lockbox (not a field office), that the address depends on the applicant's state, and that originals stay with the applicant until the interview prevents the most common mailing errors.
Source: USCIS Application Guide (2025)
