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Filing Guide
Where to Mail Your N-400 Application (2026)
If you are filing a paper N-400 (Application for Naturalization), you must mail it to the correct USCIS lockbox facility. Sending your application to the wrong address can delay your case by weeks or result in rejection. This guide covers the current lockbox addresses, the difference between USPS and courier delivery, and tips for making sure your application arrives safely.
Addresses change. USCIS periodically updates lockbox addresses. The addresses on this page reflect USCIS guidance as of early 2025. Always verify the current mailing address at uscis.gov/n-400 before mailing your application.
What Is a USCIS Lockbox Facility?
USCIS does not accept N-400 applications at local field offices. Instead, all paper filings are sent to centralized lockbox facilities operated by the U.S. Department of the Treasury. These facilities receive your application package, deposit your filing fee, issue your receipt notice (Form I-797C), and forward your case to the appropriate USCIS service center for processing.
Because lockbox facilities are high-volume processing centers, they have strict requirements about address formatting and delivery method. Using the wrong address type (for example, sending a courier package to the P.O. Box) will result in your application being returned.
N-400 Lockbox Mailing Addresses
As of early 2025, USCIS directs all N-400 paper filings to the Dallas, Texas lockbox regardless of the applicant's state of residence. Previously, filings were split between two regional lockbox locations, but USCIS has consolidated N-400 processing to a single facility. This can change at any time, so always confirm at uscis.gov/n-400.
USPS Mailing Address
Use this address for U.S. Postal Service delivery (First Class, Priority Mail, Certified Mail, etc.)
P.O. Box 660060
Dallas, TX 75266
Applies to all U.S. states and territories. Do not use this address for FedEx, UPS, or DHL — private couriers cannot deliver to P.O. Boxes.
Courier Address (FedEx, UPS, DHL)
Use this street address for private courier and express delivery services
Attn: N-400
2501 S. State Hwy. 121, Suite 400
Lewisville, TX 75067
Applies to all U.S. states and territories. Do not use this address for USPS mail — use the P.O. Box address above instead.
Which address should I use? If you are sending via USPS (including Certified Mail or Priority Mail), use the P.O. Box address. If you are sending via FedEx, UPS, DHL, or any other private courier, use the street address. Using the wrong address type for your carrier will result in non-delivery.
Special Filing Situations
Certain applicants have different filing requirements. If any of the following apply to you, do not use the standard lockbox addresses above without checking the USCIS website for updated instructions.
U.S. Military Service Members
Current members of the U.S. Armed Forces filing under INA Section 328 or 329 (naturalization through military service) should file through the USCIS military help line and may use a different filing address. Active-duty applicants stationed overseas may also have special provisions. Contact the USCIS military services unit at 877-CIS-4MIL (877-247-4645) for the correct filing address and fee exemption guidance.
Applicants Residing Outside the United States
If you are a permanent resident living abroad (for example, married to a U.S. citizen employed overseas), you may need to file at the USCIS office with jurisdiction over your location rather than a domestic lockbox. Check the USCIS N-400 instructions for overseas filing guidance, or contact the nearest U.S. embassy or consulate.
Applicants in U.S. Territories
Residents of Guam (GU), the U.S. Virgin Islands, American Samoa (AS), and the Commonwealth of the Northern Mariana Islands (CNMI) file at the same Dallas lockbox as of early 2025. However, these addresses have changed in the past. If you reside in a U.S. territory, verify the filing address at uscis.gov/n-400 before mailing.
Tips for Mailing Your N-400 Safely
Your N-400 application package contains personal information and a filing fee. Treat it like the important legal document it is. Follow these tips to protect your filing:
Use a trackable delivery method
Whether you use USPS Certified Mail, Priority Mail, or a private courier like FedEx or UPS, make sure you have a tracking number. Keep it until you receive your I-797C receipt notice from USCIS (typically 2 to 4 weeks after delivery).
Keep a complete photocopy
Before sealing the envelope, photocopy every page of your completed N-400 and all supporting documents. If your package is lost in transit or USCIS needs clarification, you will have a backup.
Never send original documents
Send photocopies of your Green Card, passport, marriage certificate, and other supporting documents. Bring the originals to your biometrics appointment and naturalization interview. USCIS will examine them in person.
Double-check the address for your delivery method
USPS mail must go to the P.O. Box address. Courier deliveries must go to the street address. Mixing these up is one of the most common filing mistakes and will cause your package to be returned.
Include Form G-1145 on top
This free, one-page form requests an email and text notification when USCIS accepts your application. Place it as the very first page of your package. See our N-400 filing checklist for the full recommended stacking order.
Do not send cash
USCIS does not accept cash payments by mail. Pay with a credit/debit card (Form G-1450), ACH bank transfer (Form G-1650), or a personal check, cashier's check, or money order (Form G-1651) payable to "U.S. Department of Homeland Security."
What Happens After You Mail Your N-400
Once the lockbox facility receives your application, the process typically follows this timeline:
- 1The lockbox receives your package, deposits your filing fee, and enters your case into the USCIS system.
- 2Within 2 to 4 weeks, you receive a receipt notice (Form I-797C) with your case number. If you filed Form G-1145, you will also get an email and text notification.
- 3USCIS schedules a biometrics appointment (fingerprints, photo, and signature) at a local Application Support Center (ASC).
- 4Your case is reviewed by the appropriate USCIS field office, and you are scheduled for a naturalization interview.
- 5At the interview, a USCIS officer reviews your application, tests your English and civics knowledge, and makes a decision on your case.
If your application is rejected (for example, due to a missing signature or incorrect fee), USCIS will return it with a letter explaining the issue. You can correct the problem and refile. For a full walkthrough of the naturalization process, see our N-400 step-by-step filing guide.
Let FormSnake Handle the Details
Worried about mailing to the wrong address? When you prepare your N-400 through FormSnake, your filing package includes a personalized instruction sheet with the correct lockbox address based on your state of residence and delivery method. The instructions are generated automatically from the latest USCIS filing guidance so you do not have to look anything up yourself.
Your complete package also includes the filled N-400 form, a personalized filing checklist, a cover letter for USCIS, and all required payment forms — everything in a single print-ready PDF. Learn more on our N-400 landing page.
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FormSnake is not a law firm and does not provide legal advice. We are not affiliated with, endorsed by, or connected to USCIS or any government agency. Use of this service does not create an attorney-client relationship. FormSnake provides self-help software for form preparation. The mailing addresses on this page are provided for general informational purposes only and reflect USCIS guidance as of early 2025. USCIS may change lockbox addresses at any time without notice. Always verify the current filing address at uscis.gov/n-400 before mailing your application. FormSnake is not responsible for applications sent to an incorrect address. If you need legal advice, consult a licensed immigration attorney. See our terms of service and privacy policy.