To send mail to a PO Box, write the recipient’s name on the first line, “PO BOX” and the box number on the second line, and the city, state and ZIP Code of the Post Office where the box is located on the last line. Send it with USPS, because UPS and FedEx can’t deliver to a standard PO Box address.
This guide shows the exact address format USPS uses, what to do when you have both a street address and a PO Box, how to send a package that won’t fit in the box, and the mistakes that get PO Box mail returned.
How Do You Address Mail to a PO Box?
A PO Box address has three lines, and the PO Box line takes the place of a street address. USPS Publication 28, the Postal Service’s addressing standard, says the box line should be written as “PO BOX” followed by the number.
Here’s the standard format:
JANE DOE PO BOX 1234 SPRINGFIELD IL 62704-1234
- Line 1, recipient: the full name of the person or business that rents the box, or someone authorized to receive mail there.
- Line 2, delivery line: “PO BOX” and the box number. USPS prefers it without periods, so write PO BOX rather than P.O. Box.
- Line 3, city line: the city, two-letter state abbreviation and ZIP Code of the Post Office that holds the box. Use the ZIP+4 if the recipient gives it to you.
The ZIP Code matters more than people expect. A PO Box often has a different ZIP Code than the recipient’s home, so use the one the box holder gave you rather than looking up their street address. Put your own return address in the top-left corner so USPS can send the piece back if something is wrong.
What If the Address Has Both a Street Address and a PO Box?
USPS delivers to whichever address sits on the line directly above the city, state and ZIP Code. Its Domestic Mail Manual says mail with both a street address and a PO Box goes to the address immediately above the city line, and to the PO Box if both appear on the same line.
Publication 28 recommends using only one address when you can. If you must include both, put the address you want the mail delivered to on the line just above the city line, and make sure the ZIP Code matches that address:
JANE DOE 456 OAK ST PO BOX 1234 SPRINGFIELD IL 62704-1234
In this example, the mail goes to PO Box 1234. Swap the two middle lines and it would go to 456 Oak St instead.
Which Carriers Can Deliver to a PO Box?
Only USPS delivers to standard PO Box addresses, because PO Boxes sit inside Post Offices. Every USPS mail class can reach one, including First-Class Mail letters, Priority Mail, Priority Mail Express and USPS Ground Advantage packages.
UPS and FedEx won’t accept a PO Box as a delivery address. A package sent with a private carrier to “PO BOX 1234” will usually be delayed, held for an address correction or returned. Our guide on how to ship a package to a PO Box covers the carrier rules in more detail.
Can a PO Box Receive UPS and FedEx Packages?
Yes, but only if the box holder signs up for USPS Street Addressing at a participating Post Office. USPS says this service gives box holders a delivery address for packages from other carriers, including Amazon, DHL, FedEx and UPS. The address combines the Post Office’s street address with the box number, for example:
JANE DOE 123 MAIN ST #1234 SPRINGFIELD IL 62704
Street Addressing isn’t available at every location, so use it only if the recipient tells you their Post Office offers it, and copy the exact format they give you.
How Do You Send a Package to a PO Box?
Send it with a USPS service and address it exactly like a letter. The steps are the same as any USPS shipment:
- Confirm the box number and ZIP Code with the recipient.
- Choose a USPS service: Ground Advantage for economy, Priority Mail for 2–3 day delivery, or Priority Mail Express for the fastest option.
- Buy and print the label, or show a USPS Label Broker code at the Post Office and the clerk prints it for you.
- Drop it at a Post Office, schedule a free USPS Package Pickup, or use a USPS collection box if the package fits the slot and carries prepaid postage.
Labels for PO Box shipments don’t need to cost the Post Office counter price. With ParcelPath, you can get up to 89% off USPS retail prices, and the service is 100% free with no subscription, label fees or minimums. Compare live USPS rates for your package in the ParcelPath rate calculator. Sellers who ship online orders face the same rule: if an eBay buyer’s shipping address is a PO Box, you’ll need to send that order with a USPS label.
What Happens When a Package Doesn’t Fit in the PO Box?
The Post Office holds it for the box holder. USPS says it leaves a slip in the box so the renter can collect the item at the counter during business hours, or places the package in a secure parcel locker at locations that have them.
Box size limits what fits. A large PO Box measures 11″ x 11″ and holds Small and Medium Flat Rate Boxes, while an extra-large box is 12″ x 22.5″. If the recipient rents a small box, expect larger packages to go to the counter.
Signature-required mail works the same way. USPS leaves a notice in the box, and the recipient signs at the counter, unless they’ve set up the free Signature on File service, which lets USPS leave the item in the box. Box holders can also preview incoming letter mail and track packages through USPS Informed Delivery.
Can You Send International Mail to a PO Box?
Yes. Mail from another country reaches a U.S. PO Box through the destination country’s postal service and then USPS, so the same three-line format works, with “USA” added as the last line. When you’re mailing from the U.S. to a PO Box abroad, follow that country’s postal format and write the country name in capital letters on the final line.
What Are the Most Common PO Box Addressing Mistakes?
Most PO Box mail that comes back has one of these problems:
- Wrong ZIP Code: using the recipient’s home ZIP Code instead of the Post Office’s.
- Missing box number: a name and “PO Box” with no number can’t be sorted.
- Two addresses in the wrong order: the line above the city line wins, so mail may go to a street address you didn’t intend.
- A private carrier label: UPS or FedEx labels addressed to a plain PO Box get stuck or returned.
- Closed or unpaid box: USPS closes a box when rent isn’t paid on time, and mail for a closed box is forwarded or returned.
If the recipient has moved or the box is closed, USPS can forward their mail for up to one year after they file a change of address.
How Is a PO Box Different From a Private Mailbox?
A PO Box is rented from USPS and sits inside a Post Office, while a private mailbox (PMB) is rented from a commercial mail receiving agency, such as a UPS Store. A private mailbox uses a street address with a “PMB” or “#” number, so it can receive packages from any carrier.
To open a private mailbox, the renter must first file USPS Form 1583, the notarized form that authorizes the operator to accept their mail. If the recipient doesn’t have a box yet, our guide on how to get a PO Box covers the application, ID requirements and rental terms, and the USPS PO Box cost guide compares box sizes. You can find the nearest Post Office that rents boxes in our USPS locations guide.
Frequently Asked Questions
Do you write P.O. Box or PO Box on an envelope?
USPS Publication 28 standardizes the line as “PO BOX” followed by the number, with no periods. Writing “P.O. Box” will still be delivered, because USPS sorting equipment reads both, but PO BOX is the official format and the safest choice for printed labels and business mail.
Can you send a package to a PO Box with UPS or FedEx?
Not to a standard PO Box address. Only USPS delivers to PO Boxes. A UPS or FedEx package can reach a box only if the box holder uses USPS Street Addressing, which pairs the Post Office’s street address with the box number and is offered at participating Post Offices only.
What ZIP Code do I use for a PO Box?
Use the ZIP Code of the Post Office where the box is located, which the box holder should give you. It’s often different from the ZIP Code of their home or business. If they give you a ZIP+4 Code for the box, include it, because it routes the mail directly to that box.
Should I put both a street address and PO Box on mail?
USPS recommends using one address. If you include both, the mail goes to the address on the line directly above the city, state and ZIP Code. Put the PO Box on that line if you want delivery to the box, and use the PO Box ZIP Code.
Sources
- USPS: PO Boxes (sizes, Street Addressing, package notices)
- USPS Publication 28, Section 28: Post Office Box Addresses
- USPS Publication 28, Section 215: Dual Addresses
- USPS Domestic Mail Manual 602.2.1: Dual addresses
Part of our USPS Locations guide. Related: USPS Shipping: Rates, Tracking & Services, USPS Collection Box.
