PO Box vs Street Address: Key Differences

Address basics  |  April 5, 2026  |  2 min read

A PO Box is a locked mailbox at a post office. A street address is a physical location where mail and packages are delivered to a door, mailroom or dock. Both are valid mailing addresses, but they behave differently.

How a PO Box is written

• JOHN DOE
• PO BOX 4521
• DENVER CO 80201

USPS prefers "PO BOX" without periods. Many post offices have their own PO Box ZIP codes that differ from the surrounding street ZIP codes.

Who can deliver

USPS delivers to PO Boxes. Private carriers generally need a street address. Some post offices offer a street addressing option for boxes so packages from other carriers can be received, but it must be set up with the post office first.

When businesses should require a street address

• Shipping with private carriers
• Services performed at a location, such as installation
• Some tax and registration forms

For billing addresses and letters, a PO Box is usually fine.

Testing both types

Forms that ship physical goods often need to detect PO Boxes. Test common spellings such as PO BOX, P.O. Box and Post Office Box, and check that legitimate street names containing "box" are not blocked by accident.

A quick comparison