How to Send Mail to a PO Box


June 13, 2023

A Post Office Box (commonly referred to as P.O. Box or PO Box) is a locked mailbox within a USPS (United States Postal Service) Post Office facility. Sending mail to a P.O. Box) can be a secure and convenient way of correspondence. 

However, if this is your first time sending mail to a P.O. Box, you may have to learn how to send the envelope correctly.  

So, you may have asked the following questions:

  • What steps do you need to follow to send mail to a P.O. Box?
  • How do you address the envelope when sending mail to a P.O. Box? What mail sizes are suitable for the P.O. Box?
  • Can you send packages or only letters to a P.O. Box? What are the processes and requirements for sending packages to a P.O. Box?
  • How can you use a P.O. Box for your business? How is a P.O. Box beneficial for you and your business?

If you want to send mail to a P.O. Box but don’t know where to start, visiting a local post office can help you with your more specific questions.

Use’s easy-to-use search tool to find the local post offices in New York, Florida, North Carolina, Georgia, Michigan, and other states. Our site offers vital information on 31,330 post offices countrywide.

In this article, you’ll learn about

  • The steps you to send mail to a P.O. Box
  • How to write a P.O. Box address
  • The mail sizes in which you can use the P.O. Box 

This article also lists and explains how to send packages to a P.O. Box, including the process and requirements for sending packages to a P.O. Box. It also explains how business owners can use the P.O. Box service to their advantage.

Steps to Ship to P.O. Boxes

The crucial difference between sending mail to a residential address and a P.O. Box is that you’ll have to write the P.O. Box number instead of the regular street address with the latter.

Here’s how you can send mail to a P.O. Box:

Choose an Envelope or Postcard

Usually, you use envelopes to send flat, flexible things, including cards, letters, forms, checks, and other paper items. 

Using a $0.63 First-Class Mail Forever stamp, you can send a 1-ounce mail anywhere in the United States. The size of 1-ounce mail can be about four sheets of regular, 8 ½ inches by 11 inches (8 ½″ ✕ 11″)  paper in a rectangular envelope.

Note that only rectangular and paper-based envelopes qualify for letter prices. 

The maximum size of the envelope should be 11 ½ ” long x 6 ⅛ ” high. For reference, a standard no. 10 envelope is 9 ½ ” long x 4 ⅛ ” high. 

You can fold the item in your envelope, but it must stay flat – no more than 1/4″ thick. 

Still, if you want to mail letter-sized papers without folding them, you can use a “flat envelope.” The postage for this large envelope begins at $1.26 for one ounce.

Also, note that if your large envelope is rigid, nonrectangular, or lumpy, you may have to pay the package price.

On the other hand, postcards are suitable for short messages that don’t require an envelope. With a $0.48 postcard stamp, you can send a standard-sized postcard to every U.S. location.

Standard postcards are typically made of paper, are between five to six inches long and 3 ½ ” to 4 ¼ ” high, and can have a 0.007″ to 0.016″ thickness.

Start at the Center of the Envelope

You should visibly write the letter’s name and address, so it’s ideal to put this information in the center of the envelope.  

You must write the recipient’s address or name to avoid the courier mishandling your letter or package. At the same time, a mistake regarding this information can cause delivery delays.

Write the Recipient’s First and Last Name on the First Line

You must include the recipient’s first and last name. Adding the recipient’s middle initial or name is an optional way to prevent having your mail intercepted by the wrong person.

 If possible, you can also add the recipient’s formal title, for example, Dr. Jane Doe. When shipping to a P.O. Box, it’s always best to be as specific as possible.

Note the Company or Organization (Optional)

This step only applies if you’re contacting a company or organization. There is a space directly beneath the recipient’s name for the company or organization’s name.

Address Your Mail

USPS prefers that you don’t include periods and commas when writing addresses. Simply use standard abbreviations in the address block, and write it as “PO BOX” (not “P.O. BOX).

Here’s how you can address your mail:

  • Envelopes: Place your return address (or sender’s address) in the upper left corner. In the bottom center, write the delivery address or recipient address.
  • Postcards: There are different formats for postcards, so specify the shipping address in the space provided. Usually, you can find this space on the same side you put your stamp and write your message.

Print your delivery and return address clearly, and correctly position them to ensure timely delivery.

Provide P.O. Box Number

Generally, P.O. Box numbers begin with the term “PO BOX,” followed by a two-to-five-digit number.

Positioning the P.O. Box Number

Another aspect that you must consider when sending mail to a P.O. Box is positioning the P.O. Box number in the address block.

Usually, the address block consists of the lines that make up a mailing address, and how you write it directly impacts how the carrier handles your mail.

Items with correctly formatted addresses are easier to sort and forward and tend to go first in the delivery process. In contrast, those with incorrectly formatted addresses tend to be put aside for later sorting.

Calculate and Apply Postage

A First-Class Mail Forever stamp can cost  $0.63 and goes in the envelope’s top right corner.

You may have to pay more if your letter exceeds the standard weight and size or if you need additional services.

On the other hand, a standard postcard stamp can cost you $0.48. However, square or large postcards can cost more. 

Remember to stamp the postcard near the delivery address using the space provided.

Where Can I Buy Postage?

Here are places where you can purchase postage:

  1. The Postal Store:  Purchase online stamps and add-on postage for heavy and oversized envelopes.
  2. Post Office Locations: Buy stamps at any post office location, self-service kiosks, or at Approved Postal Providers, including drug and grocery stores.

Additional Postage

Remember that if your envelope’s weight exceeds one ounce, you must buy additional postage.

Every extra ounce costs $0.24 for letters up to 3.5 ounces and large envelopes up to 13 ounces.

On the other hand, nonmachinable items, such as lumpy or rigid envelopes, clasps, strings, or buttons, will cost $0.40 more. In addition, your envelopes will cost more if they are square or vertical (taller than they are wide).

Lastly, you can buy 1¢, 2¢, 3¢, 5¢, and 10¢ stamps at The Postal Store.

Add-On Services

You’ll have to pay an extra fee if you want proof of delivery, insurance, signature services, or other optional features.

The USPS’ Insurance & Extra Services page can provide specific details on those additional features. Meanwhile, some of the typical letter add-on services include

  • Certified Mail: You get proof of mailing and delivery of your item.
  • Registered Mail: A recipient must sign for the mail to confirm delivery.
  • Return Receipt: You’ll receive a delivery record that shows the recipient’s signature in print or via email.
  • Adult Signature Required: The mail can only be signed for by an adult (21+) with valid government identification.

Affix A Valid Stamp

Cover the delivery costs by adding a stamp or prepaid shipping label in the upper right corner. Check the postal stamp to ensure it does not overlap with the address or other delivery information. 

Calculate your letter’s cost using a calculator, or contact your local post office for more information.

Send Your Mail

Suppose you have the correct addresses and postage on your envelope or postcard. In that case, you can send it several ways, including mailing it in your mailbox, dropping it off at the Post Office, or putting it in a blue collection box. 

A blue collection box is a painted street box with the all-familiar USPS logo. The public uses this box to deposit mail.

Here are some ways to send your mail:

  • Place your letter inside your mailbox and raise the box’s flag (if it has one).
  • Place your mail in the outgoing mail slot in a cluster mailbox.
  • Put your mail in the blue collection box.
  • Bring your mail to a post office lobby drop.

Note that if your envelope has postage stamps and weighs more than 10 ounces or is thicker than ½ inch, you can’t put it in a collection box. In this case, you must give it to an employee at a post office location. 

You Can Also Drop Mail in the “Outgoing Mail” Slot in Your Building’s Cluster Box

 If you reside in an apartment complex, you may have a cluster of mailboxes where you receive mail and packages. Each cluster box has an “outgoing mail” slot or several slots, depending on your complex’s size.  

You can drop your outgoing mail into these slots if you have attached the proper postage amount.

What Is a P.O. Box?

P.O. Box is the abbreviation for post office box, also known as a postal box. A P.O. Box is a lockable box at a post office with a unique address. 

An individual or company can rent a P.O. Box. The agreement term varies by location and size, while the cost depends on the size. 

Generally, courier service providers do not deliver to P.O. Box addresses, but there are some exceptions. 

What Is a P.O. Box Address?

P.O. Box addresses are the addresses of numbered boxes in post offices that hold the correspondence of a specific individual or organization. These addresses are usually 2-5 digit numbers indicating the postal box’s location.

What Should You Keep in Mind When Renting a P.O. Box?

Here are tips for renting a P.O. Box for the first time:

  • You need a physical address to register a company, not a P.O. Box.
  • Your P.O. Box can quickly fill up depending on its size. Empty it regularly to avoid overflowing.
  • Visits to your P.O. Box may take a lot of time, depending on the location.

How to Write P.O. Box Addresses: Format and Guidelines

The mailing process to a P.O. Box at USPS is manageable as long as you know where to fill out the address and what information to include. Here are some crucial reminders when writing a P.O. Box address:

Address Format Tips

  • Print addresses clearly in capital letters
  • If possible, include the ZIP+4 code
  • You can use a pen or a permanent marker when writing the P.O. Box address
  • Avoid using commas or periods

Writing Down the P.O. Box Designations – The Don’ts

When you write an address and see that a P.O. Box number has an indication, such as BIN, CALLER, and others, omit them immediately.

For instance, write PO BOX M instead of BIN M when addressing an outgoing letter or mail.

Write Sender’s Address

The top-left corner should contain your address (the return address). Separate the following information into separate lines:

  • Your company’s name or your full name
  • Apartment number
  • Full street address
  • City, state, and ZIP+4 code

Write the Recipient’s Address in the Middle

Place the recipient’s address in the middle of the mail. 

The first address line should have the recipient’s first and last name and the company/organization’s name below the recipient’s. Afterward, you need to write the P.O. Box number.

Add City, State, and Postal Code to the Bottom Line

Lastly, you must address a letter or package to a P.O. Box. 

Special U.S. Addresses

Below are some examples of other U.S. addresses:

Puerto Rico

This location’s addresses may include an urbanization or community code specific to an area or development. A URB code should appear on four lines in an address, as in the following example:

    150 CALLE A
    SAN JUAN PR 00926-3232

U.S. Virgin Islands

This region’s addresses have a similar format as standard addresses. The official abbreviation for the Virgin Islands is “VI.”

Military and Diplomatic Mail: APO, FPO, and DPO

Different rules apply to mail sent to military and diplomatic addresses

Don’t include the city or country name when sending something to an APO (Army Post Office), FDO (Fleet Post Office), or DPO (Diplomatic Post Office) address abroad. This step prevents foreign mail networks from receiving your mail. If you have unit and box numbers, include them:

    UNIT 100100 BOX 4120
    FPO AP 96691

Provide the Return Address

The return address for your postal mail must appear on the upper left corner of your package. 

You must always include the return address on all postal mail you send out as a business or corporate entity because it tells the recipient who you are and allows them to return the mail if it is undeliverable. 

Your company’s postal address database is valuable information, so you should find out what it contains.

Double-Check the Address Information Before You Send the Mail

Take the time to read everything you have written on the envelope carefully. When you’ve checked the delivery and return addresses, you can send the mail to one of the box locations at the post office.

Consider automating your direct mail if you handle large volumes. In this case, you’ll no longer have to write mailing addresses manually, carry mail to the U.S. Postal Service, and handle the delivery.  

Abbreviations and Periods

When addressing a P.O. Box, it is best to avoid abbreviations and periods.

The USPS suggests omitting all periods and commas when writing addresses and using standard abbreviations. 

How Do P.O. Boxes Work, and What Sizes of Mail Are They Suitable For?

If you’re mailing to a P.O. Box or arranging one for yourself, you need to understand how it works. Managing a P.O. Box is simple, but there are still some rules and limitations. 

You can rent a P.O. Box from the post office if you need a dedicated location to receive mail. However, there are some mail size restrictions for P.O. Boxes. The post office’s size restriction may vary, so it’s best to check with them for more information.

The largest P.O. Box size at USPS has a dimension of 22 ½ ” x 12″ x 14 ¾ “.

The Working of P.O. Boxes and Their Requirements

It would help to understand how a P.O. Box works when dealing with postal deliveries to P.O. Boxes, especially in large numbers like those in offices and businesses. 

Some rules and regulations apply to P.O. Box addresses, but this does not mean they are complicated tools.

Sending Packages Is a Different Story: How To Send Packages to a Post Office Box

It’s easy for beginners to confuse mailing with shipping, but the two services differ. 

The process of sending mail involves sending lightweight letters and documents covered by First Class Stamps.  

On the other hand, sending packages involves parcels usually enclosed in boxes or poly mailers.

In addition, unlike regular mail, USPS may only pick up your package if you schedule it. The institution prefers that people schedule package pickups in advance so that postal workers may plan their routes appropriately.

For instance, they may park their truck closer to your house before walking around the neighborhood, so they can pick up your package and put it in the truck as soon as they arrive.

Prepare Packages for Transport

Preparing the package for rigorous handling procedures is essential whether you’re sending it across town or overseas. Allow some room for cushioning or bracing in your boxes. Also, remember to tape the seams of each box.

Address the Packages

If you send a package to a P.O. Box, only include a street address in the mailing address if the recipient is instructed to do so. Instead, enter the customer’s name, address, city, zip code, or postal code. 

Affix the Correct Postage

Mailing packages to P.O. Boxes via USPS may cost the same as home delivery. You may benefit from USPS bulk shipping discounts if you ship in bulk.

The shipping cost depends on weight, so a parcel scale can help you calculate postage if you receive many product orders.

Send by Mail

Unlike courier services, the U.S. Postal Service can handle all packages addressed to P.O. Box addresses. 

Meanwhile, having an employee bring outgoing packages to the local post office is a good idea if you don’t have time to do it yourself. 

Alternatively, entrepreneurs can request package pickups from their warehouse or office by signing up for a USPS account. 

Usually, you can pick up the packages after the carrier delivers your mail.

Presorting Your Outgoing Mail

Saving money wherever you can is an excellent strategy for business owners. 

Having your letters and packages sorted before a mail carrier or employee picks them up or drops them off at a post office can help you save on mail service.  

It is not necessary to separate packages going to P.O. Boxes from those going to home addresses. So, you can group them by ZIP or postal code if they match. 

In the long run, it can benefit your business’ bottom line to find even small ways to cut operating costs.

P.O. Box Business Use Cases: Benefits of Mailing to a P.O. Box Over Using a Street Address

Here are some ways businesses can benefit from using P.O. Boxes


Mailing to a P.O. Box can make your startup look more professional while keeping your home address private. 

You can use a box rental for official correspondence if you do not have a business address. Maintaining your reputation while communicating with potential customers and partners through direct mail is easy with direct mail.

Financial Organizations

Institutions such as banks, insurers, debt collectors, and others often prefer to mail critical communications to a P.O. Box rather than to a regular street address. 

The location of P.O. Boxes in post offices makes them more secure than street mailboxes. Mail confidential documents or notices to a P.O. Box if you need to send them.

Online Businesses

Startups, eCommerce businesses, and other digital enterprises don’t always have physical addresses. However, they still receive print communications and need reliable contact information. 

By getting a personal box, you can get well-protected storage for your business communications at your nearest post office.

Business Owners That Frequently Travel

When you mail to a P.O. Box, you can grab your mail and packages whenever you want. Rental P.O. Boxes are a great way to keep your letters secure and private while away from home.

Dealing With P.O. Box Designations

If you notice a P.O. Box number with a designation, such as CALLER, DRAWER, or BIN, omit it from the envelope.

Improving Legibility and Efficiency

Writing addresses by hand seems impractical for businesses since they receive and send a lot of mail. Printing address labels improves the readability of addresses and decreases workload. 

Use USPS’s Click-N-Ship feature to print priority mail labels, buy stamps, and select preferred languages for your international customers.

These tools assist you in polishing your professional image and, more importantly, earn you more time to grow your business.

The Restrictions on Shipping to P.O. Boxes

It can be a hassle to ship to P.O. Boxes because only some companies can ship to P.O. Boxes. In addition, there are limitations on the size of parcels that these carriers can deliver.

Challenges of Shipping to P.O. Boxes

Here are some challenges you may encounter when shipping to P.O. Boxes:

  • Limited courier option: In the U.S., FedEx SmartPost is the only courier that delivers to P.O. Boxes other than USPS. You can ship your order to your P.O. Box by using USPS for the final leg of delivery.
  • Tricky tracking: Occasionally, shipments sit in P.O. Boxes for a while, so tracking updates would only appear once the recipient picks them up. It can be frustrating for merchants to check if their customers have received their orders.
  • International shipping can be a hassle: FedEx Express ships to some international locations and Puerto Rico. However, you will need to provide a valid phone or fax number.

How to Improve Legibility and Efficiency of Your Postal Mails

Businesses and corporations receive and send many postal mails, so handwriting these addresses can be impractical.

Additionally, the receiver or USPS personnel may need help reading the postal mail, eventually affecting deliverability. 

Consequently, consider using a printer to make address labels. In addition to improving readability, this option can also improve workload efficiency.

If you have a USPS account, you can use the Click-N-Ship feature. Additionally, you can use this tool to buy stamps and to set the preferred language for international customers.


  1. How do you send Certified Mail?

The first step to sending Certified Mail is to buy a Certified Mail slip that you’ll attach to your First-Class Mail envelope.

 If you complete the Certified Mail slip online, you may be requested to give proof of identity. Then, you’ll need to choose a USPS delivery option.

  1. Can you send Certified Mail to a P.O. Box?

Yes. Mail carriers place delivery notifications in P.O. Boxes, informing the recipient to show the delivery slip to the window clerk when Certified Mail arrives.

 Note that a recipient is not legally required to sign the delivery slip no matter where the mailpiece arrives.

  1. What are the rules and regulations regarding owning a P.O. Box?

P.O. Box regulations vary from country to country. For example, each country may differ regarding what kind of ID you need when renting a P.O. Box or how many people can access your P.O. Box. 

Your local post office can provide details regarding your region.

  1. Will shipping a parcel or a package to a P.O. Box work?

Yes. A P.O. Box is ideal for receiving mail or envelopes. However, note that the parcel’s or package’s dimensions might not fit inside the P.O. Box.

In such cases, you’ll get a notification indicating that the post office is keeping the parcel.

  1. When can courier companies deliver to P.O. Box addresses?

The delivery time varies depending on the company’s operating hours. 

Major carrier companies can deliver to P.O. Box addresses in various places worldwide, including the U.S., France, Greece, Croatia, Iceland, Portugal, and the Middle East region. 

  1. Why don’t all the couriers deliver to P.O. Boxes?

Due to certain limitations, not all courier companies can deliver to P.O. Box addresses.

Some courier companies, including UPS or FedEx, can deliver to P.O. Box addresses but only in certain countries and under specific conditions. 

For instance, the courier can arrange delivery at a different location if the consignee’s phone number is included on the shipping label.

When local or national postal offices have special agreements with courier providers, they may even deliver directly to P.O. Boxes.

  1. What are some alternatives to P.O. Box delivery?

P.O. Boxes provide permanent addresses and secure delivery at the local post office for the receiver.

However, alternative options are available if P.O. Box delivery could be better for your situation.

For example, you can always provide the address of a friend or neighbor if you’re concerned you would not be able to pick up your package at the delivery address or your address is difficult to locate.

At the same time, if you spend most of your time at the office delivering your parcel, letting the receptionist know in advance can help avoid misunderstandings.


  1. How to Send a Letter or Postcard: Domestic
  2. Manage P.O. Box Sizes