Nothing is 100% – PBSAs

By Adam Collinson

There’s one rule I always go back to in address quality: nothing is 100%.

For every pattern we learn, there’s an exception — and often, without exception, there are also exceptions to the exceptions.

Let’s talk about one of the more nuanced exceptions: PO Box Street Address (PBSA) equivalents.

CMRA vs. PBSA: The Background

To understand PBSAs, it helps to start with Commercial Mail Receiving Agencies (CMRAs). These are non-USPS businesses that offer mailbox rentals — think UPS Store, Mail Boxes Etc., or your local pack-and-ship, but there are even some self-storage facilities and also offer CMRA services. Unlike USPS PO Boxes, CMRAs:

• • Often have extended hours
    
  • May be more conveniently located
    
  • Accept deliveries from non-USPS carriers
    
  • May provide additional services, including
    • Open, image, and make available electronically
    • Upon request, forward to another address
  • Provide addresses that appear to be standard street addresses

This last point — the appearance of a physical address — introduces both compliance risk and fraud potential, particularly for industries with strict regulatory obligations. We’ll tackle that in a future article.

To compete with CMRAs, the USPS created PO Box Street Address (PBSA) equivalents — a way to make a traditional PO Box act, or at least look, more like a street address. The PBSA format uses the street address of the Post Office, plus a unit number that corresponds to a PO BOX number:

123 MAIN ST UNIT 4567 → PBSA for PO BOX 4567 in the post office at 123 MAIN ST

Seems simple, but again: nothing is 100%.

 

PBSA: What’s Really Happening?

First, not all PO BOX’s have a PBSA.  As of April 2025:

• • There are over 22 million PO Boxes across 30,683 facilities
    
  • Roughly 11 million boxes across 8,615 Post Offices are deemed competitive (i.e., located near a CMRA) and therefore eligible for PBSA services

When a customer rents a PBSA-eligible box:

• • They pay a higher rate to cover expanded services
    
  • USPS accepts deliveries from other carriers (FedEx, UPS, etc.)
    
  • Final delivery is still handled through USPS PO BOX services

But here’s the key operational nuance:

Delivery from the private carrier to the Post Office is not delivery to the recipient.

Tracking from the original carrier ends at handoff. In some cases, the USPS may use a signature on file — meaning that even if a delivery record shows as “signed,” the recipient may not have signed for anything at all.

The Address Quality Challenges

From a data perspective, PBSAs are tricky because the address looks like a standard multi-unit dwelling:

12 1ST AVE UNIT 20

That could be:

• • A genuine unit in a complex
    
  • A CMRA location (with the actual recipient renting PMB 20)
    
  • A USPS PBSA address that maps back to a PO BOX
    • NOTE: while the UNIT number is typically the same value as the PO Box number – exceptions exist.
      
  • A completely invalid UNIT (e.g., UNIT 20 doesn’t exist, but the carrier assumes it’s a PMB value and delivers to the “UNIT” number occupied by the CMRA in that complex)

Add in the fact that identifiers like “PMB,” “STE,” “APT,” and “#” are often used interchangeably or inconsistently, and suddenly it becomes harder to distinguish a physical address from a proxy (non-physical) address.

COA Complications

Change of Address (COA) processing further muddies the waters:

• • You cannot file a COA to a PBSA format — it must go to the PO Box format instead
  • You must file a COA from a PBSA address in addition to the PO Box format

If you’re managing compliance workflows, this is a landmine. Many regulated industries — financial services, telecom, healthcare — prohibit the use of non-physical addresses in specific scenarios. A PBSA, by design, is a non-physical address, and flagging it correctly is essential.

What You See Isn’t Always What You Get

The bottom line? You can’t always trust what an address looks like.

That’s why basic visual parsing or format checks aren’t enough. Detecting PBSAs, CMRAs, and other non-standard addresses requires deeper analysis — beyond the printed line on a mailpiece.

This is just one example of why address quality is never black-and-white.

In my next article, we’ll explore another common pitfall where appearances can deceive.