Tracked mail: scan in the box. Accountable mail: signature at the counter.
What each USPS service returns on a PO Box lane
| Service | What the sender sees | Includes signature |
|---|---|---|
| Priority Mail, Ground Advantage, First-Class Package | Delivered scan with the local Post Office scan point | No, unless Signature Confirmation is added |
| Priority Mail Express | Delivered scan; signature captured on retrieval unless waived by shipper or by Signature on File | Yes by default |
| Signature Confirmation | Delivered scan plus a captured signature returned through Track & Confirm | Yes |
| Certified Mail with Return Receipt | Delivered scan and PS Form 3811 (green card) returned by mail, or an electronic Return Receipt | Yes |
| Registered Mail | Delivered scan plus a full custody trail and captured signature at retrieval | Yes |
How the PO Box mechanics work
USPS treats the PO Box as the delivery point. Small parcels go into the box; oversized ones go into a parcel locker with a key or notice card left in the box; accountable mail (signature required) triggers PS Form 3849, the notice card that tells the holder to see the counter with identification.
- The delivered scan for a plain tracked parcel is written when the carrier scans the barcode at the box or at the parcel locker, not at the moment the holder retrieves it.
- For signature-required mail, the scan is written when the box holder signs at the counter. That may be hours or days after the parcel physically arrived at the Post Office.
- The Post Office holds accountable mail for the retention window (usually 15 days), then returns it as unclaimed. The sender's tracking then reads “unclaimed”.
Signature on File shortens the trip
USPS offers PO Box holders a Signature on File option: the holder signs one form at the Post Office, and future signature-required mail is placed directly in the box or a parcel locker instead of triggering a counter visit. The sender's proof of delivery references the filed signature rather than a per-parcel counter signature.
Sellers who need a per-parcel signature for chargeback protection should be aware that Signature on File on the recipient's box means the proof of delivery for a Signature Confirmation parcel does not show a fresh handwritten line for that shipment. It is the filed signature, dated at file time. For a hostile chargeback, USPS's electronic delivery record and the box holder's Signature on File are still what USPS returns.
The FedEx and UPS side
Neither carrier delivers to a USPS PO Box. A FedEx or UPS label with a PO Box address either returns to sender or is refused at pickup. No proof of delivery is produced. The workaround is USPS Street Addressing where the PO Box holder's Post Office publishes a street address that FedEx and UPS accept; the carrier delivers to that street address and USPS routes to the box. In that case FedEx or UPS returns its own delivery record for the Post Office street address, and USPS routing to the box is invisible to the sender's tracking.
Where these rules come from
- USPS, USPS Mail Requiring a Signature — Accountable Mail — the notice card process and Signature on File. Read 2026-08-11.
- USPS, What is Signature Confirmation — how the electronic signature is returned. Read 2026-08-11.
- USPS, Publication 370 — Signature Confirmation — PO Box delivery mechanics and retention. Read 2026-08-11.
- USPS, PS Form 3849 Redelivery Notice. Read 2026-08-11.
Common questions
Does USPS get a proof of delivery for a PO Box?
Yes. A tracking-enabled service records a delivered scan when the parcel is placed in the box, and a signature service records a signature when the box holder collects the item at the counter.
How is a signature captured on a PO Box delivery?
USPS leaves PS Form 3849 in the box. The holder brings it to the counter, presents identification and signs there. The signature is scanned to the tracking event and returned to the sender through the proof-of-delivery request.
What is Signature on File and how does it change things?
Signature on File is a USPS PO Box option that files a one-time signature with the Post Office. Signature-required parcels are then placed directly in the box or a parcel locker without a counter visit. The sender's proof of delivery references the filed signature, not a per-parcel one.
Can FedEx or UPS deliver to a PO Box with proof of delivery?
No. FedEx and UPS are not authorised to deliver to a USPS PO Box. A FedEx or UPS label to a PO Box does not deliver, and no proof of delivery is generated. USPS Street Addressing lets a box holder receive from either carrier at a Post Office street address instead.
How long can I retrieve the signature record?
USPS keeps the electronic delivery record and any captured signature under Publication 370 retention rules. Signature and delivery records for Signature Confirmation are retained for two years.