Tracking Numbers what's the odds?

So today I noticed that we have had the same tracking numbers for 3 different orders.
USPS Reusing Tracking.
1st gap 8 months
2nd gap 7 months
I guess I’ll be seeing it again in 6 months

Considering how many packages are shipped in a day in the US, and the fact that the tracking numbers aren’t actually random, I’d say decent odds.


Yeah and they don’t seem to randomize them, USPS seems to just cycle through them


I knew they got reused.
I figured It would be re-using random tracking numbers that others have used.
Now it looks like they are giving us our own tracking “range” so to speak.

We use Endicia, maybe that has something to do with it?

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It could be, kinda like the first X digits of Fedex and UPS are your account number


USPS tracking numbers are 22 digits.

The first five digits comprise the service code. The first 2 numbers tell where/how the label was printed.

  • 91 (legacy/other)
  • 92 and 93 Commercial Mailers
  • 94 Electronic (From the users device)
  • 95 Made at the Post Office

The next 3 digits state the type of service the package is being sent.

  • USPS Tracking: 001
  • Priority Mail: 055
  • Certified Mail: 073
  • Registered Mail: 088
  • Signature Confirmation: 021

USPS has published a full list of services in USPS Publication 199

The next 2 numbers indicate the sender. And the last 6 numbers are the account number given to the business or individual if they have an account with USPS or if not it is randomly given.

USPS delivers approximately 20.5 million packages daily. With nine undefined (to my knowledge) numbers remaining that gives us 1 trillion combinations, or 48 days worth of unique tracking numbers.

Of course this breaks down if USPS assigns tracking to individual accounts/services, etc.

But essentially, yes to recycing tracking numbers,


Last year at the USPS website, I read tracking numbers were recyclef after 5 months.


There are a limited number of tracking numbers, how often they get recycled would depend on how many packages are shipped. I assume 5 months is an average based on all possible shipping methods and options, with some being used less often than others. I imagine that signature required labels are cycled at a slower rate than standard Priority labels, for example.



I just found this on the USPS tracking page, there’s a drop down below the delivery status that has the info and links. It appears to be only for the specific order though and I don’t know if it has to be purchased before delivery or if it might be available longer - in case of an INR could there be time to purchase the extension if you sense trouble.

USPS Tracking Plus® [mod edit: added FAQ link]

Your item is eligible for USPS Tracking Plus. This feature allows you to buy extended access to your tracking history and receive a statement via email upon request. Without this feature, your regular tracking history is only available on this site until November 3, 2023. To extend your access to this tracking history, select the length of time you would like and confirm your selection. You can only purchase extended history once, so all orders are final and are not eligible for a refund.

Note: For multiple tracking numbers, you can save and continue adding USPS Tracking Plus selections to your cart until you are ready to complete your purchase.

6 Months
1 Year
3 Years
5 Years
7 Years
10 Years
[mod edit: removed links to live tracking]


Yes, but not exclusive of Endicia as this could happen with any of the label providers including Amazon.

USPS prepares us for this as a tracking number’s information is no longer available online to see after 90 days. Within that 90 days, you can purchase a hold on the tracking info with

This basically puts that tracking number out of the recycle for the period purchased.

As it is currently designed by USPS, it is probably safe to say you will not see the same tracking number sooner than 6 months.

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Well, unless Amazon sticks its sticky fingers into the pie, as is being reported in two recent SAS threads (as well as in at least two recent NSFE discussions, here & here):

Our friend @packetfire’s from 25Dec23 here:

and our friend @Canadianmag’s from 27Dec23 here:

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