What a PO Box is
A Post Office Box is a lockable mailbox located at a post office. People and organizations may use one when they prefer to collect mail at a postal facility rather than receive it at a street address.
Why a PO Box may have a distinct ZIP Code
Some post offices use ZIP Codes or delivery arrangements dedicated to PO Box service. The correct code depends on the post office and the box address, so a nearby street ZIP Code should not be substituted automatically.
Address formatting
A PO Box mailing address normally includes the recipient, the words PO BOX followed by the box number, and the city, state and ZIP Code. Follow the exact format provided by the post office or the recipient.
Verify before sending
Use the complete PO Box address when checking postal information. A general city lookup may not reveal the correct code for a specific box.