Box number, nothing else
Name, then the box number as the holder wrote it, then city, state and ZIP. A street address added out of politeness gives the sorting equipment two destinations to choose between.
Proof of delivery
Certified mail to a PO Box: yes, with a different ending
A box number is a perfectly good address for certified mail, and it is one of the few destinations where the postal service is the only option rather than the cheapest one. The part worth understanding before you seal the envelope is the handover: nobody signs at a bank of boxes, so a notice goes into the box, the piece waits behind the counter, and the date on your record is the date the holder walked in. Rules on this page were read at pe.usps.com on 2026-07-28.
Manual sections cited15 day clock explainedRead 2026-07-28
No door, no doorstep
The signature moves from the point of delivery to the retail counter, and the clock starts when the notice lands in the box.
Why the answer is yes
Certified Mail is not a class of mail. It is an extra service bought on top of postage, so the question is only whether the underlying class reaches a box, and it does. Five points from the rulebook settle the whole thing.
| The question | What the manual says | Section |
|---|---|---|
| Is a box number a real address? | A box customer receives "any mail properly addressed to the box number" | DMM 508.4.3.1 |
| Which classes carry the service? | Certified Mail is available on First-Class Mail and Priority Mail | DMM 503, Exhibit 1.4.1 |
| What does the fee buy? | A mailing receipt, and a record of delivery that includes the recipient's signature | DMM 503.3.1.1 |
| Does it cover loss or damage? | No indemnity comes with it, beyond whatever the underlying Priority Mail already carries | DMM 503.3.1.1 |
| What if it cannot be handed over? | "A notice is provided to the addressee for a mailpiece that cannot be delivered", and the piece goes back to the sender after 15 days | DMM 508.1.1.7 |
That last row is the one doing the work here. A piece requiring a signature cannot be completed at a locked box, so the notice rule is not an exception at a PO Box, it is the normal path. Everything below follows from it.
What changes when the address is a box
The signature moves to the counter
At a street address the carrier collects the signature at the door and the record closes there. At a box there is nobody to hand the letter to, so the piece stays behind the retail window and the holder signs when they arrive. The evidence you end up with is the same kind of evidence; it is created in a different place, by a person who chose the moment.
The wait is not the transit time
Tracking may sit still for a week and mean nothing at all is wrong. A box holder who checks the mail on Saturdays collects on Saturday, and the scan that closes the record appears then. Sending a letter on Monday and phoning the recipient on Thursday about the silence is a conversation nobody needs.
Fifteen days, then it comes home
The manual gives 15 days from the notice before an unclaimed piece is returned to the sender, with 5 days for Priority Mail Express and 10 for COD. Put that against any deadline you are working to. If a notice has to be received a fortnight before a date, posting it a fortnight before that date is cutting it very fine indeed.
An unclaimed return is still information
A letter that comes back untouched proves the attempt and the notice rather than the reading. Leases, statutes and court rules take different views on what that is worth, and the person to ask is whoever wrote the requirement you are trying to satisfy. Nothing on a shipping site should be read as an answer to that question.
Getting the envelope right
Your return address matters more here
Fifteen days after the notice, an uncollected piece is coming back to whatever address is in the top left corner. Make sure it is one you still open.
The counter step is unavoidable
The certified form carries an article number that a retail employee round-dates when the piece is accepted, which is why this is not something any online checkout can produce, ours included.
If a named person must sign
Restricted Delivery is a separate add-on in the same part of the manual, and it narrows who is allowed to sign for the piece. It is a different product from certified mail, priced separately.
When the thing you are sending is not paper
A fair share of the people asking this question want to send an object to somebody who only gave them a box number. Certified mail is the wrong shape for that job: it is built for documents, its scan trail is thin, and it carries no protection for what is inside. A tracked parcel label does the delivery, and a signature service does the proof.
The constraint is the address, not the price. A bare box number can only be served by the postal service, so the comparison stops being a comparison and the postal rate is the rate. Where the recipient has street addressing arranged with their Post Office, every carrier is back in play and the board opens up again.
Certified mail and PO Boxes, answered
Can you send certified mail to a PO Box?
Yes. Certified Mail is bought on top of First-Class Mail or Priority Mail, both of which USPS carries to box numbers, and the Domestic Mail Manual says a box customer receives any mail properly addressed to the box number. The address that stops a courier label is one the postal service was always able to reach.
Who signs for it when the address is a box?
The box holder does, at the counter. There is no doorstep at a bank of boxes and no carrier standing there with a scanner, so the piece is kept behind the window and a notice is put in the box instead. The signature happens when the holder comes to collect.
How long will the Post Office hold it?
Fifteen days. DMM 508.1.1.7 states that a notice is provided for a piece that cannot be delivered, and that if it is not called for the piece goes back to the sender after 15 days. Priority Mail Express is 5 days and COD is 10.
What delivery date will the record show?
The day the holder came to the window, not the day the letter reached the building. Anyone counting a deadline from the delivery date is counting from a date the recipient controls, which is the single practical difference between a box and a street address.
Can I send a parcel to a PO Box the same way?
Only through the postal service. A bare box number is not an address a private carrier can deliver to, so a parcel bound for one has to travel on a USPS label unless the holder has street addressing set up with their Post Office.