I'm working on a shipping tracking number library and would like to add support for OnTrac.
Based on some sample numbers (e.g. C10999911320231, C10999606576777, C11001105367744), the format seems to be a C followed by 14 digits, where the first digit is always a 1. Are there other formats?
There also appears to be a checksum, as Google only recognizes certain variations (e.g. C10999911320231 works, but C10999911320232 does not). I tried various algorithms but couldn't work it out. How is the checksum calculated?
A tracking number is a C followed by 14 digits, where the last digit is the check-digit. The check-digit calculation is identical to UPS, including converting the C to a 4. Thanks to Danielle at OnTrac for providing this information.