The USPS samples for domestic services show a package tracking number of 22 digits: 9400 1000 0000 0000 0000 00 for USPS Tracking, 9205 5000 0000 0000 0000 00 for Priority Mail, 9407 3000 0000 0000 0000 00 for Certified Mail. The USPS tracking page lists a sample next to each service. International services look different: the sample for Priority Mail Express International is EC 000 000 000 US.
UPS, postal and container numbers each have their own shape
The UPS tracking support page lists four formats: 1Z followed by 16 characters (18 in all), 12 digits, a T plus 10 digits, and 9 digits.
The UPU’s S10 standard covers items that need individual tracking, such as EMS items, parcels, and registered, tracked and insured letter-post items. The specification fixes 13 characters for them: two letters for the service, an eight-digit serial number, one check digit, and a two-letter country code of the issuing country. USPS’s sample EC 000 000 000 US for Priority Mail Express International ends in US for that reason.
Ocean freight tracks the container itself. BIC describes the container code as a three-letter owner or operator code, a fourth letter as equipment identifier, a six-digit serial number and a seventh check digit. The example on its page is BICU 123456 5. BIC’s example is labelled theoretical. The last digit gives a system a way to validate the recording and transmission accuracy of the code. Navo’s container tracking takes a container number, bill of lading or booking number. With only the paper in hand, the bill of lading route works too.
Getting the number
The sender receives it. USPS says the tracking number is generated and provided to the sender, and that Care Center agents and local Post Offices cannot help recover a lost one, so a recipient can ask the sender. USPS also points to Informed Delivery, which shows most domestic packages tied to the address on a USPS.com account. Some mail has none: postcards and First-Class Mail letters without extra services.
USPS lists the places to find the package tracking number: the Post Office shipping receipt, the sales receipt if you bought insurance, the USPS.com confirmation email, the retailer’s shipping confirmation email, and the peel-off portion of the label.
What the carrier’s rules say when the history stops
A correct number with a frozen history goes to the carrier’s own process. UPS says to file a claim if a package “has gone days without a scan or says delivered but you can’t find it.” USPS accepts a Missing Mail search request from 7 days after mailing up to 365 days after it, and asks for both addresses, the mailing date and the tracking number where there is one. USPS says it sometimes cannot find missing items. An insured item may also be claimable, no later than 60 days from mailing.
What a Nashville audit found about Delivered scans
The USPS Office of Inspector General audited the Church Street Station in Nashville, Tennessee, and published report 26-110-1-R26 in September 2026. Between March 1 and May 31, 2026, employees improperly scanned 176 packages at the delivery unit itself. About 73 percent of those scans read “Delivered.” The auditors also reviewed 121 scans made more than 1,000 feet from the delivery point, after removing scans that could have been within policy. Roughly 60 percent of those read “Delivered” too.
Then the auditors went in on the morning of July 14, 2026, before carriers arrived for the day, and pulled 30 packages from the carrier cases. Twenty-one (70 percent) had improper scans or handling issues. Thirteen carried a “Delivered” scan, which should follow only a package left at the customer’s address.
This is one station, and the report covers only it. A Delivered scan with no parcel at the door can come from a scan made in the wrong place. If that happens, the options above apply: a search request, and a claim if the item was insured.
Frequently asked questions
What goes into a Missing Mail request besides the addresses?
USPS asks for the size and type of the container or envelope, the mailing date from your mailing receipt or Click-N-Ship label, and a description of the contents (what it is, plus brand, model, color or size if relevant). Pictures that could help identify the item are requested too.
What happens after I file a Missing Mail request?
USPS sends a confirmation email and periodic updates about the search. A found item goes to the address you gave. Some items are not recovered because it was not safe to forward them. With a money-back guarantee such as Priority Mail Express, a refund request may be possible.
Which organizations accept the BIC container code?
BIC's page lists the World Customs Organization, the International Road Transport Union, the International Union of Railways, the International Chamber of Shipping, IATA and FIDI.