A. You must be 18 years or older to apply for a PO Box online. Your ID will be verified at the Post Office. If you are under 18 years of age and want a PO Box, see the local Post Office for the guidelines. For more information and additional FAQs about PO Boxes Online, go to www.usps.com/poboxes.
https://about.usps.com/postal-bulletin/2008/html/pb22239/html/POBoxkit_004.html