PMB and CMRA private mailbox addresses

A private mailbox is the CMRA’s street address plus PMB or #, so a PO BOX keyword does not match it

Direct answer. A private mailbox (PMB) is a box rented from a private company. USPS Publication 28, section 285, says those companies are commercial mail receiving agencies (CMRA), and that 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. The same section says the words POST OFFICE BOX or PO BOX and the private mailbox number cannot be used on the Delivery Address Line, that only the Postal Service is entitled to provide delivery to a PO Box, and that the Delivery Address Line is the standardized address of the private company. Domestic Mail Manual 602, section 2.3, says mail sent to an addressee at a CMRA must be addressed to their private mailbox (“PMB” or “#”) number at the CMRA mailing address. Section 1.3 of that same DMM part lists the private mailbox designator before the street and number. A checkout rule that looks for the letters PO BOX is aimed at a Post Office box line. Section 285 says that line is not how the private mailbox is written. This page is not legal advice.

PO Box Blocker — AddressFence (Shopify App Store · Write a review). Free blocks PO Boxes and parcel lockers on the shipping address at checkout, plus a small set of ZIP rules. Street-number checks and billing-address rules are on a paid plan. It lets you test any address in the simulator before publishing, with one-click rollback. It does not say the app detects a PMB or a CMRA. This page is the USPS private-mailbox format — not a list of strings the app matches.

Related: B2B PO Guard — Require PO — B2B purchase order number required at company checkout.

Free check first: PO box and street number address checker runs in your browser and sends nothing. Paste addresses and see which look like a PO box or lack a street number.

Checklist before you treat the line as a PO Box

The format section 285 and DMM 602 require

Section 285 says either a three-line or a four-line address format can be used with a CMRA address and the PMB or # identifier, with one exception. Where the CMRA’s physical address requires its own secondary address element, the PMB or # address must follow the format rules on that page. It is not permissible to combine the secondary address element of the mailing address for the CMRA and the CMRA customer’s private box number. The exception on that page: when the CMRA mailing address contains a secondary address element (for example a rural route box number, suite, #, or other term), the CMRA customer must use PMB when utilizing a three-line address format. The examples themselves are on the Publication 28 page. This page does not redraw them.

DMM 602, section 1.3, lists the delivery-address elements in order, including the private mailbox designator (“PMB” or alternative “#”) and number if the mailpiece is addressed to a CMRA address, then the street and number. Section 1.4.2 includes, among complete-address elements, the private mail box designator and number, and the page’s parenthetical is “PMB 300 or #300”. The same subsection says “PO Box” is used incorrectly if preceding a private box number. Section 2.3 is the short CMRA rule: the mailpiece is addressed to the private mailbox (“PMB” or “#”) number at the CMRA mailing address.

Why that line is not a USPS PO Box

Publication 28 section 281 standardizes a Post Office box as PO BOX plus the number. That job is US PO Box address format, including Street Addressing where the Postal Service offers it. Section 285 is the private company. It says the Delivery Address Line is the standardized address of the private company, and that POST OFFICE BOX or PO BOX cannot be used with the private mailbox number on that line. A shopper can therefore type a street, a suite that belongs to the CMRA, and PMB or #. A rule that matches only the PO BOX keyword does not see that street line. Whether UPS will deliver to a Post Office box is a different page: Does UPS deliver to a US PO Box? Whether Shopify checkout ships to a PO Box is Does Shopify ship to PO Boxes? Holding an order after checkout is Hold PO box ship-to orders billed to a commercial suite. That page is a hold. It is not this format.

What this page is not

Related pages

Not legal advice. Confirm Publication 28 section 285 and DMM 602 sections 1.3, 1.4.2, and 2.3 before you treat a street line with PMB or # as a Post Office box. The app checks billing-address rules you publish. The listing does not say it detects a private mailbox.