You sign up for a business address, the welcome email arrives, and there it is: "2125 Biscayne Blvd, Suite 300 #1234." Then the questions start. Is the "#" part of the street number? Does Suite 300 mean I have an office? And why does this online form keep rejecting the pound sign?
All fair questions. That little "#" comes with a USPS rule, a bit of history and a few habits worth knowing. Here they are in plain words.
One note first. #1234 is just an example on this page. Your real mailbox number is the one in your account.
The words behind the address
USPS is the United States Postal Service, the national mail service.
A CMRA, or commercial mail receiving agency, is a private business that accepts mail from USPS for its customers, then holds it or sends it on (USPS CMRA FAQ). Virtual mailboxes, virtual offices and shipping-store mailboxes are all CMRAs in postal terms, whatever their websites call them. Prima is one too.
PMB stands for private mailbox. It's the label USPS uses for a customer's box at a CMRA.
So what does PMB mean in an address?
It tells the post office, and anyone reading, that the address is a private mailbox at a mail receiving business. USPS rules say mail for a CMRA customer has to carry either "PMB" or the "#" sign, followed by the mailbox number (DMM 508, section 1.8). The DMM is the Domestic Mail Manual, the rulebook USPS writes for mail.
USPS made "PMB" mandatory in 1999 so the public could tell when an address was a private mailbox rather than a physical office. A year later it let customers use "#" instead, as a middle ground between consumer protection and small businesses (Federal Register, August 2000). Both mean exactly the same thing.
And no other label is allowed. USPS's addressing guide, Publication 28, says a private mailbox can't be dressed up as "Suite," "Apt." or "Unit," and you can't write "P.O. Box" in front of the number either (Publication 28, section 285).
Reading "2125 Biscayne Blvd, Suite 300 #1234"
- 2125 Biscayne Blvd is the building's street address in Miami.
- Suite 300 is part of the address where mail is delivered, and it's the same for every customer.
- #1234 is your mailbox number. It's the part that tells our team the letter is yours.
That's why we always say "mailbox number" and never "your own suite." You get a real address in a real office building, with mail handled by people on site. You don't get a private office behind a door with your name on it, and calling it a suite would be both against USPS rules and not quite honest.
How to write it on forms and envelopes
Write it the way it appears in your account, with the street, the suite and your mailbox number together:
- Your name or company name
- 2125 Biscayne Blvd, Suite 300 #1234
- Miami, FL 33137
If a form gives you a second address line, "2125 Biscayne Blvd" can go on the first and "Suite 300 #1234" on the second. Either way, keep the "#" and the number together.
A few things to avoid:
- Merging the numbers. "Suite 300-1234" or "Suite 3001234" looks tidy, but USPS Publication 28 says the building's suite and your box number can't be combined.
- Dropping the number. This is the big one. More below.
- Writing "Suite 1234." It isn't a suite.
What about forms that reject the "#" sign? Write "PMB 1234" instead. USPS treats the two the same, and "PMB" has no special characters. What matters most is that the number makes it onto the envelope.
Why mail without the number can come back
USPS delivers a CMRA's mail to the business as a whole, and then the CMRA sorts it to each customer. Your number is how a letter finds you. Without it, someone has to match the letter by name alone, and a common name, a typo or a company name you've changed can turn that into a guess. USPS has also said that a cluttered address line can trip up its automated sorting machines (Federal Register, March 2000).
There's a stricter rule behind it. A CMRA can only accept mail for people and companies with a signed PS Form 1583 on file. If a letter arrives for someone who isn't on a form, it has to go back to the Post Office as undeliverable (DMM 508).
PS Form 1583 and the ID check
PS Form 1583 is a short USPS form that authorizes a CMRA to receive mail in your name. Think of it as a permission slip with ID attached.
You show two IDs: one photo ID, like a passport or a driver's license, and one document that proves where you live, like a lease or a vehicle registration (USPS acceptable ID). Then you sign in front of the CMRA's staff, in person or on a live video call, or in front of a notary commissioned in the US. A notary is an official who confirms you are who you say you are when you sign.
Two habits save trouble later. List your company on the form, so mail addressed to the business is covered. And add anyone else who'll get mail there, like a cofounder. At Prima you sign the form on a quick video call with an online notary, included in every plan. Our Form 1583 guide goes step by step.
What it means for your Florida LLC on Sunbiz
Sunbiz is the Florida state website where LLCs are registered, and the record it shows is public. Florida asks for a few different addresses, and the PMB plays differently on each.
- Mailing address: a clean fit. Florida even allows a P.O. box here, so a street address with a mailbox number is well within the rules.
- Principal office: a gray area. This line must be a street address and it means the place the business is actually run from. No official Florida source we've found says whether an address with a PMB or "#" counts. We explain the whole question in our guide on using a virtual office as your LLC's address.
- Registered agent: no. That's the person or company that accepts lawsuits for your LLC, and Florida wants someone physically there during business hours. Prima doesn't offer that service.
Don't try to hide the PMB
It's tempting to drop the number so the address looks like a regular office. Please don't. Your mail is the first thing to suffer.
And it doesn't fool anyone who checks. USPS keeps its own registry of mailbox customers, and some banks and payment companies screen for mailbox addresses. Stripe, the online payments company, now returns a specific error for CMRA addresses on some account types (Stripe changelog). Each bank and platform sets its own rules, so ask them first.
Honestly, a private mailbox is nothing to apologize for. It's a real Florida business address, a virtual address that keeps your home off public records, and a perfectly ordinary way for a small business to get its mail.
Where Prima fits
Prima's Address plan is a virtual mailbox: a business address at 2125 Biscayne Blvd, your mailbox number, every envelope photographed in the app, and open-and-scans at $2.50 each when you need to read one. Today it's $39 a month (see current prices). When you need more, like a Miami phone number or packages, the same address grows into a virtual office on the Business and Executive plans. See what a virtual mailbox in Florida looks like with us, or compare it with a P.O. box, a shipping-store mailbox and coworking in Miami. If you're setting up a Florida LLC, start with a business address for your Florida LLC.