Can an expired passport be renewed by mail?

The short answer is "It depends." Passports issued to minors cannot be renewed by mail independent of whether they have expired or not. Expired passports that were issued to applicants ages 16 or older can be renewed by mail as long as 1) the passport is not significantly damaged; 2) the applicant can submit the expired passport with the application and supporting documents; and 3) it has not been expired for more than 5 years. A quick look at the expiration date will let you know if you can still renew your passport by mail or not.

Source: http://www.us-passport-service-guide.com/expired-passport.html

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