I have heard of great confusion being caused by UPS reusing old tracking numbers. A 16 character string that can include letters should provide a vast amount before having to use the same one twice. Of course, some of the digits could be checksums, or location/service based. How many possible tracking numbers are there really?
with UPS, only the last 8 characters are the actual package identifier. the first six characters after “1Z” are the shipper’s account code.
But would that mean that at least for each shipper account, there are 10[sup]8[/sup] = 100 million different numbers available? For each service level (as indicated on the Wiki article), that is, i.e. 100 million for next day, another 100 million for second day, another 100 million for regular ground delivery, etc.?
According to their own website, they can reuse numbers after 6 months, if need be. Unless I’m misinterpreting the information on that page, which I will concede is certainly a possibility.
According to this article citing 2015 stats, Amazon on behalf of sellers shipped 2 billion packages in 2015 and over 200 million Amazon Prime packages that holiday season.
Not all UPS, possibly not all domestic US, etc. But it seems Amazon can use up an 8 digit block in not too much time. Even giving Amazon a few extra shipping codes isn’t going to help in the long term.
Possibly (00000000-99999999) but that assumes none of them are “special” like check digits.
I had assumed there was one but the Wikipedia article doesn’t mention it. OTOH, the system the USPS (and other postal services) uses does mention a check digit.
I do a lot of shipping for the company I work for, and for our account the numbers are assigned sequentially. Digits 11-17 started with 0000001 and are now somewhere up around 0016800. The final digit does appear to be a check sum.