The Problem with SKU-Only Thinking

Most warehouse software manages inventory as a list of product quantities distributed across locations: "you have 500 units of Product A spread across your warehouse." That number is useful for financial reporting, but it tells you almost nothing about where those 500 units physically are right now, whether they are mixed with other products on a pallet, which lot numbers they carry, when they expire, or which specific bin to open when you need to pick 50 of them.

When a picker needs those 50 units, the system can point to a general location — but if that location holds multiple products, multiple pallets, and multiple lot numbers, the picker still has to search manually. Errors follow. The wrong lot is picked, an earlier expiry date is missed, or a picker takes items from a pallet that is already reserved for a different order. These errors happen not because people are careless but because the system gives them insufficient information.

eWAVE's answer is the License Plate Number: a unique identifier that attaches to a physical container and travels with it through every stage of the warehouse lifecycle.

What is an LPN?

An LPN is a barcode label attached to a physical container — a pallet, a tote, a carton, or even an individual item where tight traceability is required. That barcode label becomes the system's unique identifier for everything on, under, or inside that container. Scan the LPN barcode and you immediately know:

• Every product on the container and its exact quantity
• Lot numbers and batch codes for each product line
• Serial numbers for individually serialised items
• Manufacturing dates and expiry dates where applicable
• Country of origin for customs and regulatory compliance
• The precise storage location of the container at that moment
• The complete movement history — every location the container has been in, from first receipt

The LPN is not just an inventory record; it is a portable, scannable summary of a physical object that follows the goods from supplier dock to customer delivery.

Example: A Mixed-SKU LPN

Consider a real-world example: a supplier ships a pallet containing three different products. With SKU-only thinking, receiving this pallet means updating three separate inventory records. If the pallet later moves to reserve storage, three more updates are needed. If it is split during picking, the system has to track three product quantities independently. With LPN thinking, all of this collapses into a single container identity:

Moving this pallet from C-07-2-A to D-12-1-A requires exactly one scan of the LPN and one scan of the destination location. All three product lines are updated in a single transaction. There is no ambiguity, no manual counting, and a full audit record is created automatically.

Container Types and LPN Applications

LPN Data Model

In eWAVE, an LPN is composed of two linked records: the LPN Header (ewave.lpn.header) and one or more LPN Detail lines (ewave.lpn.details). The header carries the container-level attributes — LPN number, current location, status, container type, and total weight. Each detail line carries one product/lot combination with its quantity, expiry date, country of origin, and any serial numbers.

This two-level structure is what enables mixed-SKU containers: a single header can have as many detail lines as there are product/lot combinations on the pallet. When the pallet moves, only the header location field changes — all detail lines move with it implicitly. When the pallet is consumed during picking, each detail line's quantity is decremented as items are removed, and the header status advances through the lifecycle accordingly.

Lot and Serial Number Integration

eWAVE captures lot numbers, serial numbers, manufacturing dates, and expiry dates at the LPN detail level, which means this traceability data is always associated with a specific physical container in a specific location. This has important operational consequences:

• FEFO picking (First Expiry, First Out): the allocation engine can be configured to prefer LPNs with the earliest expiry date when multiple LPNs of the same product are available. This prevents expiry date violations without relying on pickers to remember the rule.
• Recall management: if a specific lot number needs to be recalled, the system immediately identifies every LPN containing that lot, its current location, whether any of it has already been picked or shipped, and which orders it was included in. A recall that might take days with a spreadsheet system takes minutes with LPN-level tracking.
• Country-of-origin compliance: for products subject to preferential tariff rules or country-of-origin declarations on shipping documents, the recorded origin on each LPN detail line can be pulled into export documentation automatically.
• Regulatory audit: for food, pharmaceutical, or cosmetics warehouses subject to regulatory inspection, the complete chain — which lot came in on which ASN, where it was stored, who moved it, which order it left on — is immediately retrievable from the transaction log.

The LPN Lifecycle

Every LPN moves through a defined set of statuses in eWAVE. Each status change is recorded as an immutable transaction in the audit log, with the user, timestamp, and location information captured automatically.

LPN Splitting and Merging

Real warehouse operations regularly require splitting or merging containers — a pallet is partially picked and the remainder needs to be labelled and returned to storage, or two small containers are combined onto a single pallet. eWAVE handles both scenarios:

• Split: when a partial quantity is removed from an LPN (during a pick or a cross-dock transfer), the system automatically creates a child LPN for the removed quantity and updates the parent LPN's detail lines with the remaining quantity. Both LPNs maintain their lot/serial linkage and full transaction history.
• Merge: two or more LPNs can be consolidated onto a single container. The system creates a new parent LPN and moves all detail lines from the source LPNs, marking the sources as consumed. The new LPN inherits the location of the first source and the merged weight and volume.