Short answer
PMB means private mailbox. It is a numbered box you rent from a private company, called a commercial mail receiving agency (CMRA), rather than from the Post Office. The U.S. Postal Service (USPS) says mail to that box must include “PMB” or the “#” sign followed by the box number, as in 10 MAIN ST PMB 234. The street address is the company’s address.
Key takeaways
- PMB means private mailbox. The box is rented from a private company that the U.S. Postal Service (USPS) calls a commercial mail receiving agency (CMRA).
- USPS Publication 28 says mail to a CMRA customer “must include either the PMB identifier or the #, followed by the appropriate private mailbox number.” The next sentence reads: “Use of any other identifier is prohibited.”
- USPS names one exception. When the company’s own address has a secondary element such as a suite, a three-line address must use PMB, as in 10 MAIN ST STE 11 PMB 234.
- A PO Box is a locked mailbox rented at a Post Office. A suite is a unit inside a building. One address can show both a suite and a PMB.
- USPS delivers the mail to the company, and the company handles the boxes. The box holder fills out PS Form 1583 and shows two forms of ID, one with a photo. Each CMRA must register with the Post Office responsible for delivery.
- A # sign alone does not prove a PMB, because # can also mark a unit or a PO Box with Street Addressing. Some rules name the PMB directly, so read the label on each line of a form.
What does PMB mean in an address?
PMB stands for private mailbox. It marks a box you rent from a private company that receives mail for customers, rather than a box at the Post Office. The U.S. Postal Service (USPS) calls that kind of company a commercial mail receiving agency, or CMRA.
USPS Publication 28 is the Postal Service’s book of addressing standards. Section 285 says: “Private companies offering mailbox rental services to individuals and businesses are considered commercial mail receiving agencies (CMRA).” The USPS help page on CMRAs says such a company accepts mail from USPS for its customers and “delivers it to a private mailbox (PMB), or re-mails it to another location of the customer’s choosing with new postage.”
An address with a PMB has two parts. The street line is the company’s location. Publication 28 says: “The Delivery Address Line is the standardized address of the private company.” The PMB number is your box at that company.
The USPS definition covers more than mailbox stores. The Domestic Mail Manual (DMM), section 508.1.8.1, defines a CMRA as “a business that, in whole or in part, accepts the delivery of U.S. Mail on behalf of another person or entity as a business service.” The same section says office business centers are “considered CMRAs for Postal Service purposes.” On that wording, a virtual mailbox company that accepts U.S. Mail for customers as a business service fits the definition too.
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How a PMB appears in an address
Publication 28, section 285, sets the label: “Mail sent to an addressee at a CMRA must include either the PMB identifier or the #, followed by the appropriate private mailbox number. Use of any other identifier is prohibited.” DMM section 508.1.8.3 agrees: “A CMRA must represent its delivery address designation for the intended addressees by the use of “PMB” (private mailbox) or the alternative “#” sign.”
So the current rule allows either label, PMB 234 or #234. USPS names one exception. When the company’s own address has a secondary element, such as a suite, the customer “must use “PMB” in the three-line format.”
The table uses the examples USPS prints in those two documents. The name line and the city line are left out.
| Format | USPS example | What USPS says |
|---|---|---|
| Four lines, with the box on its own line | PMB 234 or #234, on the line above 10 MAIN ST STE 11 | Allowed |
| Three lines, with the box on the street line | 10 MAIN ST PMB 234 or 10 MAIN ST #234 | Allowed when the company’s address has no secondary element |
| Three lines, and the company’s address has a suite | 10 MAIN ST STE 11 PMB 234 | The customer “must use “PMB” in the three-line format” |
| Suite and box number joined together | 10 MAIN ST STE 11-234 | “It is not permissible to combine” the two |
| Pound sign after a suite on one line | 10 MAIN ST STE 11 # 234 | Publication 28 marks this example “Unacceptable” |
From DMM section 508.1.8.3 and Publication 28, section 285, read on November 7, 2026.
The label matters for delivery. The DMM says: “The USPS may return mail without a proper address to the sender endorsed “Undeliverable as Addressed, Missing PMB or # Sign.”” If your address is a private mailbox, keep the PMB or # on the address you give out. The company also writes your complete delivery address on PS Form 1583, so ask for that exact line and copy it.
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PMB vs PO Box vs Suite
These three labels name different things. The table compares them, and the two paragraphs after it explain how a PMB differs from a PO Box and from a suite.
| Question | PMB | PO Box | Suite |
|---|---|---|---|
| What it names | A mailbox at a private company | A locked mailbox at a Post Office | A unit inside a building |
| Who provides it | A private company (a CMRA) | USPS | Whoever owns or leases the unit |
| How it is written | PMB 234 or #234, with the company’s street address | PO BOX 1234 | STE 11, after the street address |
| Form for the service | PS Form 1583, kept by the company | PS Form 1093, filed with USPS | No USPS mailbox form |
A PMB and a PO Box come from two different providers. Publication 28 says: “Only the Postal Service is entitled to provide delivery to a PO Box.” A standard PO Box address reads PO BOX and a number. Some Post Offices also offer an option that uses the Post Office’s street address with a “#” sign or “UNIT” and the box number. That form can look like a suite or a PMB, and our guide on how to tell if an address is a PO Box explains how to spot it.
A PMB and a suite are also different, and one address can show both. In the USPS example 10 MAIN ST STE 11 PMB 234, STE 11 is part of the company’s own address and PMB 234 is the customer’s box. Publication 28 says “Use of any other identifier is prohibited,” so a private mailbox number takes PMB or # and no other word.
Does USPS deliver to a PMB?
USPS delivers to the company, and the company handles the boxes. The USPS help page says: “The United States Postal Service delivers all of a CMRA customer’s mail to the CMRA, but is not responsible for putting the mail in the individual boxes.” The same page says to “Contact the CMRA directly” about delivery issues.
Registered Mail has its own rule. The USPS help page says: “You must go to the local Post Office to accept Registered Mail. A CMRA may accept other Accountable Mail.”
The USPS pages in this guide cover U.S. Mail. For packages from UPS or FedEx, ask the company that runs the mailbox which carriers it accepts.
If you are choosing an address for general business mail, ask how you will get your mail, who to contact about a missing item, and what happens when you leave. Our Silicon Valley and Los Angeles pages describe the business addresses save office offers.
What a CMRA must do and what you file
USPS sets duties for both sides. The list gives the main points.
- The company registers. The DMM says: “Each CMRA must register with the Post Office responsible for delivery.” The owner or manager provides PS Form 1583-A to the postmaster or a designee.
- The box holder applies. The USPS help page says customers “will be required to fill out PS Form 1583.” The next line reads: “Two forms of ID (one with a photo) are required when applying for a Private Mail Box.”
- The company keeps the record. The DMM says the CMRA must keep at least a digital copy of the completed form at its business location.
- Changes need a new form. The DMM says: “When any information required on PS Form 1583 changes, the addressee must complete a new application with the CMRA.”
The form affects delivery. If the company has no Form 1583 on file for you, the DMM says it must return your mail to the Post Office. Our guide to filling out USPS Form 1583 goes through each box, the IDs, and who signs for a business.
Closing a PMB has its own rule. The USPS help page says: “The CMRA is responsible for forwarding their customers’ mail for 6 months following PMB termination. USPS cannot process a change of address request from a CMRA to another address.”
A CMRA record tells you that the business falls under these USPS rules. Our guide to what a non-CMRA address means explains what that record does and does not decide.
How to tell if an address is a PMB
Start with the address line. If the line does not answer the question, use the other checks.
- 1Read the line. “PMB” and a number show the address is written as a private mailbox.
- 2Treat a # sign as a clue only. The DMM lets a CMRA use #. Publication 28 also lets # stand for a unit, and says it “should not be used as a secondary unit designator if the correct designation, such as APT or STE, is known or is shown in the ZIP+4 file.” A PO Box with Street Addressing can use # as well.
- 3Look up the USPS record. USPS address data includes a CMRA table. Our guide on how to check if an address is a CMRA shows how to look up any address.
- 4Check your own paperwork. If you filled out PS Form 1583 to get the address, you get mail there through a CMRA. The form defines the agent as “The Commercial Mail Receiving Agency (CMRA)” and has a line for the “PMB #.”
- 5Ask the company. Ask whether the location is a CMRA and how USPS expects the box number to be written.
The word Suite on a page does not answer the question either, because anyone can type that word. Use the lookup if the answer matters to you.
Can you use a PMB as a business address?
You can receive general business mail at a PMB. Whether a PMB fits a line on a form depends on that line, so read its label first.
Some rules name the PMB in their own words. Washington’s Secretary of State says: “The Principal Office address must be the street address of the business. A PO BOX or PMB cannot be used for the physical address requirement but can be provided as an alternate mailing address.” Shopify’s account setup page says: “You can’t use PO Box or Private Mail Box addresses with Shopify Payments.”
These two rules are examples, and other agencies and platforms use other words. A rule that names a PMB does not tell you which other addresses are approved, so ask the agency or platform if the label leaves you unsure. Check any address you choose against the wording of each rule, and that includes a save office address.
Not legal or tax advice
This guide summarizes USPS Publication 28, section 508 of the Domestic Mail Manual, the USPS CMRA help page, and PS Form 1583. The guide also summarizes pages from the Washington Secretary of State and Shopify. All were read on November 7, 2026. These rules can change. Check the current page before you rely on it, and ask a professional about your situation.
Frequently Asked Questions
Sources & References
Primary sources this guide is based on.
- 1USPS Postal Explorer · Publication 28, Section 285: Private Mailbox Addresses (accessed November 7, 2026)
- 2USPS Postal Explorer · Domestic Mail Manual, Section 508: Recipient Services (accessed November 7, 2026)
- 3United States Postal Service · Commercial Mail Receiving Agency (CMRA) (accessed November 7, 2026)
- 4United States Postal Service · PS Form 1583, Application for Delivery of Mail Through Agent (accessed November 7, 2026)
- 5USPS Postal Explorer · Publication 28, Section 213: Secondary Address Unit Designators (accessed November 7, 2026)
- 6USPS Postal Explorer · Publication 28, Section 281: Post Office Box Address Format (accessed November 7, 2026)
- 7USPS Postal Explorer · Publication 28, Section 284: PO Box Street Addressing (accessed November 7, 2026)
- 8United States Postal Service · Rent a PO Box (accessed November 7, 2026)
- 9USPS PostalPro · DPV (Delivery Point Validation) (accessed November 7, 2026)
- 10Washington Secretary of State · Contact Information Requirements and Updates (accessed November 7, 2026)
- 11Shopify Help Center · Shopify Payments account setup (accessed November 7, 2026)
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