How to calculate a FedEx Smartpost tracking number' check digit

Question

FedEx Ground's tracking numbers have different digits: 12, 15, 20, 22.

12-digits tracking numbers use mod 11 algorithm. Others use mod 10 algorithm.

But recently I got some 20-digits FedEx Smartpost tracking numbers which can't identified by both algorithms.

So, how can I identify these tracking numbers?

Sample tracking numbers: 7489999873402038xxxx 6129270107532465xxxx

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I figured this out.

see: http://images.fedex.com/us/software/pdf/FedEx_SmartPost_Job_Aid_v2600_06222012.pdf https://www.pdffiller.com/en/project/10655396.htm

22 digits tracking numbers remove 2 digits application identifiers (91 or 92). We need add application identifiers to the tracking numbers before mod 10 algorithm.

Answer 1

The 20 digit codes need either 91 (old) or 92 (new) before the code. Pre-pend those and apply a standard mod-10 algorithm used by the IMpb standard.