Overview
When a single Fulfillment Order ships in more than one box, Luminous creates a separate label — and a separate tracking number — for every parcel. All of the labels produced in one print action are linked together so you can manage, reprint, or void the whole group at once.
What happens when you print a multi-package label
- You specify the parcels — each box's weight and dimensions are submitted together in a single print request.
- Luminous calls your carrier once for the entire group. The carrier returns one label per parcel.
- Each parcel gets its own row in Luminous's label store, containing:
- Its own tracking number (what you'd give the customer or put on the box).
- Its own label image (PDF or ZPL), available for 24 hours for reprinting.
- A sequence number (1, 2, 3 … N) indicating its position in the group.
- All rows are stamped with a shared group identifier so Luminous knows they belong to the same shipment event.
Master tracking numbers (FedEx & UPS)
FedEx and UPS use a multi-piece shipment model: in addition to the individual tracking number on every box, the carrier assigns one master tracking number that represents the entire shipment. Luminous stores this master tracking number alongside each parcel's individual number.
For other supported carriers (EasyPost, USPS, DHL), there is no master tracking number — each parcel is treated as an independent shipment by the carrier, and only the per-parcel tracking number is stored.
How the Fulfillment Order is marked shipped
After all parcel labels are purchased successfully, Luminous automatically flips the Fulfillment Order status to Shipped and records the tracking information. This triggers the same side-effects as any other shipment (inventory updates, invoice creation, and — depending on your push settings — sending tracking to your sales channel such as Shopify).
Reprinting labels
Each parcel's label is stored for 24 hours from the time it was first printed. Within that window, clicking Reprint fetches the stored label without contacting the carrier again — no duplicate charge. After 24 hours the stored label data is purged and reprinting is no longer available.
Voiding a multi-package shipment
Voiding works at the group level: cancelling one parcel cancels all parcels that were printed together.
- FedEx / UPS: Luminous sends a single cancellation request to the carrier (using the master tracking number), then marks every parcel row as voided locally.
- EasyPost / USPS / DHL: Luminous sends a separate void request to the carrier for each parcel row.
Voiding also happens automatically if the Fulfillment Order is cancelled — Luminous voids every outstanding label for that order and records the reason "Auto-voided: fulfillment order cancelled."
Idempotency — no accidental double charges
Before contacting the carrier, Luminous computes a fingerprint for each parcel based on the Fulfillment Order, carrier account, service, weight, dimensions, ship date, and parcel sequence. If a matching, non-voided label already exists in the store, Luminous returns the cached label immediately — the carrier is never called a second time and your account is not charged again. This protects against duplicate prints caused by network retries or accidental double-clicks.
Summary
| What | How Luminous handles it |
|---|---|
| Tracking numbers | One per parcel; stored in Luminous and returned to the UI |
| Master tracking (FedEx/UPS) | One master number stored alongside every parcel row |
| Grouping | All parcels from one print share a group ID |
| Label storage | 24-hour window; reprint without re-charging the carrier |
| Voiding | Entire group voided together; one carrier call for master-tracked carriers |
| Duplicate protection | Fingerprint check before every carrier call |
For general label printing setup (connecting a carrier account, mapping shipping services, bulk printing), see Label Printing: Print Shipping Labels Directly from Luminous.