Canadian · Validation
S10 tracking number checker.
Check the 13-character number on an international postal item, like RR123456785CA — its format, its check digit, and what the two-letter service code means.
What a pass means: an S10 number is 2 letters, 8 digits, 1 check digit and a 2-letter country code. A pass means the check digit matches the 8 digits — it does not confirm the number was issued, that a parcel exists, or who it belongs to. This tool cannot track a parcel.
Inputs
Result
Enter a tracking number and press Check.
How the S10 check digit works
The Universal Postal Union's S10 standard defines the 13-character identifier used on international postal items: a 2-letter service indicator, an 8-digit serial number, one check digit, and the 2-letter ISO 3166 code of the issuing country, for example RR123456785CA.
To compute the check digit, multiply the 8 serial digits left to right by 8, 6, 4, 2, 3, 5, 9, 7 and add them up (S). The check digit is 11 − (S mod 11), except that 10 becomes 0 and 11 becomes 5. The letters are ignored in the arithmetic.
Worked example: RR287043775IN has serial 28704377. S = 2×8 + 8×6 + 7×4 + 0×2 + 4×3 + 3×5 + 7×9 + 7×7 = 231. 231 mod 11 = 0, so 11 − 0 = 11, which becomes 5. The number's check digit is 5, so it passes.
The first service-indicator letter follows the S10 list: for example C parcel post, E EMS, L tracked letter post, R registered letter post, U letter post without customer tracking, V insured letter post. Some ranges are reserved or for domestic and bilateral use only, and the tool says so. The country code is only checked to be two letters; it is not looked up.
Sources: UPU standard S10-12 (upu.int), and the jkeen/tracking_number_data reference data, which agree on the weights and the modulo-11 rule.
Format check — not tracking
This tool checks format and check digit only. It cannot look up a parcel, show its location or status, or confirm that the number was issued or belongs to anyone. To track an item, use the website of the postal service that issued it (the last two letters show the country). Nothing you type is transmitted, stored, or logged.