Services like AfterShip or Tracktry use import codes in their batch endpoints. A POST request to /v1/trackings/import might require a poly_code field that concatenates carrier_slug + tracking_number + customer_tag . This prevents duplicate entries and enables partial updates.
This article provides a technical yet accessible breakdown of what Poly Track Import Codes are, how they function, and where they are most commonly deployed. poly track import codes
"carrier": "usps", "tracking": "9405510200883184056789", "reference": "RET-001" Services like AfterShip or Tracktry use import codes