Officially, USPS recommends shipping your package as close to the Ship Date on the label as possible.
In most cases, packages shipped within a few days of the Ship Date are accepted without issue, though acceptance is solely up to the discretion of the USPS worker/branch location.
However, USPS shipping labels are only valid for a limited time (generally up to 28–30 days from the Ship Date). If a label is used well beyond this timeframe, USPS may treat it as invalid or unpaid postage, and the package could be refused, returned, or confiscated.
In addition, the USPS tracking page only shows results when:
The tracking number is recognized as valid
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AND it has been accepted into USPS systems in a normal way.
Shipments with an older ship date, but still accepted by USPS, may still still scan internally with USPS, but may no longer be recognized as valid prepaid postage causing the USPS tracking display to be suppressed.
If either of those fails, you may get the following message when attempting to track the shipment on the USPS Tracking page: “Tracking Not Available-Tracking is not available for this item. This may be because the tracking number is invalid; USPS has not yet received payment; USPS has not yet received the item; the item does not include tracking; or other reasons.”
If you need to postdate a shipment to be sent at a later date, you can select a ship date for up to 30 days for USPS shipments.
If you created a label with an earlier ship date that you were unable to send, we recommend voiding the label to prevent any delay or rejection of your shipment and using the Edit and Reship feature to create a new label with the correct ship date.
Note: Descartes XPS Ship will not take responsibility for any rejected, returned, or confiscated packages USPS considers invalid due to a significantly older ship date
Additional Help Center articles you may want to review: