Locating the post office box of a person or fellow business can be as simple as picking up the phone and asking for it. You can also track it down online. Although the term "P.O. box" is commonly associated with the mailboxes available at the post office, this is not the only place where mailboxes are rented. Private businesses rent out mailboxes as well, and the box number can be included in the address as a P.O. box number or attached to the street address as an apartment or suite number. For example, a private mailbox can be addressed as P.O. Box 12345, Los Angeles, CA 90018 or 100 Anywhere Street #12345, Los Angeles, CA 90018.

Your Own Mailbox  

If you've forgotten or misplaced your business's mailbox number – it happens, especially if you're busy starting a new venture, or "reviving" an old one – visit the location where you opened the box and ask for it. You will likely be asked to verify your identity by providing photo identification, such as a driver's license or passport. If this is not possible, call the facility instead. Depending on their policy, you may be able to verify your identity over the phone by answering questions or be required to mail or fax a copy of your identification documents before the facility releases the information. If your mailbox is located at the post office, you can access the United States Postal Service online or by phone at 1-800-275-8777.

Individual's Mailbox 

Locating another person's mailbox number may be a challenge, depending on the circumstances. If your relationship is a friendly one, call or email the person it belongs to and ask for it. Maybe you've done business with the person in the past, and have his or her phone number or email address in your contact list. If you don't have a relationship with the person, start your search by reviewing any personal websites and social media accounts he or she may have online. The mailbox address may be listed in one of his or her online profiles. You can also call 411 Directory Assistance. Although routinely used for business contact information, it also provides phone and address information for individuals. If online and 411 searches are unsuccessful, you can try a people finder service, such as Intelius and People Smart, usually for a fee.

Business Mailbox 

There are a variety of ways to determine a business's mailbox number. The quickest option is to visit the company's website. The mailbox number is likely listed on the "Contact Us" page or in the footer area alongside the company's address and phone numbers. If a mailbox number is not listed, call the business and obtain the address from company personnel. If the business is required to register with the state, you can also obtain the address from the secretary of state or registrar's office in the county where the business operates.

Mailboxes at the Post Office

If you believe a person or business has a mailbox at the post office, you may be able to obtain the mailbox number by submitting a Freedom of Information Act (FOIA) request to the U.S. Postal Service. Your request must be in writing and clearly labeled as an FOIA request. If you know the specific postal facility where the mailbox is located, mail it to the postmaster at that location. If you don't know this information, mail it to USPS headquarters at:

Managers Records Office
U.S. Postal Service
47 L'Enfant Plaza SW, Room 4541
Washington, D.C. 20260-2201

You can also fax the request to (202) 268-5353. Headquarters will route your request to the proper facility. Make sure to provide your name, mailing address and a detailed description of the information you are seeking. It can take up to 20 business days to receive a written response from USPS. There is no charge for this service.


The U.S. Postal Service usually will not disclose a post office box address without the permission of the owner. There are some circumstances under which it will release the information without permission, but these usually require a subpoena or court order. The Address Disclosure Chart (Exhibit 5-2A) on the USPS website identifies the circumstances under which you can obtain another party's post office box address.