Tracking number formats: what RB123456785CN and others mean

Some tracking numbers follow an international standard and carry a little information in their letters; others are just a carrier's internal serial. Here is how to read the common ones, and what they can't tell you.

International postal numbers (UPU S10)

Postal services around the world number their tracked items with a format defined by the Universal Postal Union in its S10 standard. An S10 number has exactly 13 characters:

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  2 letters: the service indicator, set by the postal operator.
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  8 digits: the serial number of the item.
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  1 digit: a check digit, calculated from the serial number (the 11th character).
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  2 letters: the ISO code of the country of the postal operator that issued the number.

So RB123456785CN is service indicator RB, serial 12345678, check digit 5, issued by the postal operator of China (CN).

What the first letters usually mean

The standard groups service indicators by kind of mail, with some codes reserved for particular uses. As a rough guide:

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  E…: EMS, the express service of postal operators.
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  C…: parcels.
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  R…: associated with registered letter-post items.
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  L…: tracked letter-post items.
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  U…: used for some other letter-post items with a barcode; the letter alone doesn't tell you how much tracking there is.

Treat these as hints, not rules. Within these ranges each postal operator assigns codes to its own products, so the same two letters can mean different services in different countries. In particular, a number starting with U doesn't always mean "untracked", and one starting with R isn't always a registered letter.

What the last two letters can and can't tell you

The country code names the postal operator that issued the number, not the place the goods came from or the seller's country. Online shops and logistics companies often send items through the postal service of another country, so a parcel from a seller in China can carry a number ending in NL, SE, SG or GB. The code helps you decide which postal service to check first. After arrival, your own national postal service can usually track the same number.

The check digit

The ninth digit is computed from the eight before it: multiply them by 8, 6, 4, 2, 3, 5, 9 and 7, add the results, and take 11 minus the remainder of the sum divided by 11 (10 becomes 0, 11 becomes 5). Trackers use it to catch many typos before asking any carrier. A correct check digit only means the number is well formed: it doesn't prove the number was issued or that a package exists. For the serial 12345678 the sum is 204, the remainder 6, so the check digit is 5.

Common courier formats

Couriers and parcel companies use their own formats. These are common shapes, not validation rules: carriers have several services and partners, so not every number of a carrier looks like this, and a number can change at a handover to a local carrier.

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  UPS: 1Z followed by 16 letters and digits, 18 characters in all. See UPS tracking.
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  FedEx: usually 12 or 15 digits; some services use longer barcodes. See FedEx tracking.
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  USPS: domestic numbers are usually 20 to 22 digits, many starting with 92, 93, 94 or 95; many international items use S10 numbers ending in US. See USPS tracking.
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  DHL Express: 10 digits. Other DHL networks use different formats; see DHL tracking.
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  Royal Mail: many tracked items use S10 numbers ending in GB. See Royal Mail tracking.
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  Evri: 16 characters, either digits only or a mix of letters and digits. See Evri tracking.
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  Cainiao: often LP followed by 14 or more digits, besides S10 numbers of partner postal services. See Cainiao tracking.
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  YunExpress: YT followed by 16 digits. See YunExpress tracking.
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  Amazon's own delivery network: often TBA followed by 12 digits. See finding Amazon tracking.

Spaces and lowercase

Labels often print numbers in groups for readability, and people type them in lowercase. Neither is part of the number: rb 1234 5678 5cn is the same as RB123456785CN. Trackful removes spaces and uppercases the letters when you paste a number, then checks it with the carriers whose formats it fits.