Usually, an address includes only a post office (P.O.) box or only a street address. When you have them both, it is important to know the proper way to include them on your correspondence so you can be sure it gets to the right place. Barry Jones, who is a U.S. Postal Service worker in Howard Lake, Minnesota, outlined how to do so.
When Sending to P.O. Box
When you know for sure you are sending something to a P.O. box, and you include the street address as extra information or as a shipping address if the P.O. box does not accept packages, it is important to put the P.O. box number first. List the recipient's name (either a person's name or a company's name), and then list the P.O. box number. After you list the P.O. box number, list the street address. The post office employees will know that the item goes to the P.O. box, but they will have the street address if something goes wrong or they need to contact the recipient.
When Sending To A Street Address
When you sending something to a particular street address but the person also has a P.O. box number, put the street address first, and then put the P.O. box number. For example, list the person's name or business' name, then list the street address, and follow on the third line with the P.O. box number. In this case, the P.O. box number is used as a "just in case" function. If mail delivery is not possible to the street address, the recipient is not home and the package needs to be signed for or there is another reason that the mail cannot get where it is going, then the P.O. box number will be used and the post office will notify the recipient that he has something in his post office box.
When You Aren't Sure
If you were given both a street address and P.O. box number for a person or business, and you aren't sure at which place the mail is received, assume that it is the P.O. box and put that number first. Write the recipient's name, then the words "PO Box" followed by the P.O. box number you were given. On the third line, use the street address. This will allow the post office and the mail carrier to deliver the item as quickly as possible.