How to Address a PO Box on an Envelope

We mail to a lot of PO Boxes, and there can be plenty of confusion about how they work. Even getting the address onto an envelope can feel more complicated than it should. Fortunately, addressing a letter to a PO Box is almost the same as addressing any other letter. Write the recipient's name first, replace the street address with the PO Box number, and finish with the city, state, and ZIP Code. There are a few details worth remembering, and I will cover those below.

The Correct PO Box Address Format

The format is pretty straightforward. The main thing to remember is that you are mailing to a box at a specific Post Office location, so confirm that you have the correct ZIP Code for that PO Box before sending the letter.

Write the address in this order:

1. The recipient's full name or business name
2. PO Box followed by the box number
3. City, two-letter state abbreviation, and ZIP Code

Formatting Rules That Matter

I am sure postal workers see PO Box addresses written a thousand different ways: P.O. Box, Post Office Box, odd capitalization, and sometimes just a box number. There is no reason to make them interpret it. USPS gives us a standard format, so I recommend using it exactly as written:

Put that line directly above the city, state, and ZIP Code. Use the ZIP Code assigned to that specific PO Box address.

Do not substitute PMB for PO Box. PMB means private mailbox and is used by commercial mailbox providers, not USPS Post Office Boxes. USPS Publication 28 specifically reserves PO BOX for Postal Service boxes.

PO Box Street Addressing

This is where PO Box addressing can get confusing. Some Post Office locations offer an optional service called Street Addressing. Instead of writing PO BOX 1234, the box holder can use the physical street address of the Post Office followed by #1234. The number after the # sign is still the same PO Box number. It is not a second address or a different box.

Street Addressing can allow the box holder to receive qualifying packages from private carriers such as UPS, FedEx, DHL, or Amazon. The ordinary PO Box address still works for USPS mail.

Ordering from Amazon? See when Amazon can deliver to a PO Box and which address to enter at checkout.

This option is not available at every Post Office. The box holder must use a participating location and complete the USPS customer agreement. Do not guess the Post Office street address or add a # number on your own. Ask the box holder for the exact address supplied by their Post Office.

Finding the Correct ZIP Code

Finding the right ZIP Code for a PO Box can be a pain, especially when a city has several Post Office locations. We built a ZIP+4 lookup tool to make it easier. Enter PO BOX followed by the box number in the Street Address field, then add the city and state. The tool can return the standardized ZIP Code and ZIP+4 when USPS has a matching address.

When accuracy really matters, confirm the result with the official USPS ZIP Code Lookup listed in the Sources section below, or call the Post Office where the box is located. Asking the box holder for their complete mailing address is still the simplest option.

Sending Packages to a PO Box

USPS can deliver packages to a PO Box, but the box itself is mainly a receptacle for everyday mail and smaller items. When a package does not fit, the customer may need to collect it through another pickup method provided by that Post Office.

One of the newer options is the USPS Smart Locker. These are secure package lockers installed at select Post Office locations. They are separate from a rented PO Box and are meant for package pickup and, at some locations, package drop-off.

For an eligible delivery, the recipient can select an available Smart Locker as the delivery location. USPS emails a QR code after the package is placed in the locker. The recipient scans that code at the locker to open the correct compartment without waiting at the retail counter.

Smart Lockers are only available at select locations, although USPS continues to add them as Post Office lobbies are modernized. Many offer access outside normal counter hours, and some are available 24 hours a day. Check the services at the specific Post Office before relying on one.

Frequently Asked Questions