What lot traceability is
A lot is a set of units produced under the same conditions, identified by a code that the manufacturer prints on the packaging. Lot traceability is the ability to follow that code in two directions:
- Backward: which supplier delivered the lot and with which document, on which date and with which expiration date.
- Forward: which locations it occupied, which orders took it and which customers received it, in which quantities.
Each company in the supply chain is responsible for its own segment: one step back and one step forward. The warehouse is not required to know how the customer used the product; it must know with certainty to whom it delivered the product and how much remains in stock.
Why it matters: product recalls and regulations
When a manufacturer detects a problem in a lot, the time needed to remove it from the market depends on how quickly each link in the chain identifies where that lot is. A warehouse that takes days to review packing slips and spreadsheets delays the entire recall.
In Mexico, the official standard NOM-251-SSA1-2009, which governs hygiene practices for processing food, beverages and dietary supplements, requires in section 6.7 a plan to withdraw any identified lot from the market, to keep the withdrawn products under supervision and custody and to keep records of each recall, including the lot of the product involved. The standard is published in Spanish in the Official Gazette of the Federation (DOF). Other industries have their own regulations and customer requirements. In every case, the basic data is the same: the lot recorded at every receipt and every shipment.
A warehouse system does not certify compliance with a regulation; compliance depends on each company's processes. What it provides is the reliable record those processes require.
What to record at each step
| Step | Minimum data | Risk if it is missing |
|---|---|---|
| Receiving | Product, lot, expiration date, quantity, supplier, document, date | The lot is in the warehouse without a known origin |
| Put-away | Lot and destination location | The lot is in the warehouse, but its location is unknown |
| Transfers | Lot, origin, destination and document | The lot is lost between warehouses or locations |
| Picking | Lot taken from each location for each order | The lot received by each customer is unknown |
| Shipping | Order, customer, dispatch date | The recipients of the lot cannot be notified |
| Returns | Returned lot and original outbound document | A recalled lot returns to available stock |
| Write-offs and shrinkage | Lot, quantity and reason | The lot's stock does not reconcile during an investigation |
The weakest point is usually picking. If the picker takes the most convenient lot and the system records the lot it allocated, the record does not match what the customer received. Scan validation of the lot at picking closes that gap.
How to capture the lot without errors: GS1-128
Entering the lot by hand at every receipt is slow and produces transcription errors. Many suppliers print a GS1-128 code on their logistics label. It combines several data elements in one barcode, each preceded by an application identifier from the GS1 standard:
- (01) GTIN: the product code.
- (10) lot number.
- (17) expiration date, in YYMMDD format.
- (21) serial number.
With a single scan, the system records the product, the lot and the expiration date, and the person only confirms the quantity. If your supplier does not print GS1-128, it can be requested in the purchase terms; GS1 Mexico administers the codes in the country. See the definition of GS1-128.
How to run a mock recall
A mock recall tests that traceability works before it is needed. Select a real lot that has already been partially shipped and follow these steps:
- Record the start time and the selected lot.
- Identify the origin: supplier, receiving document, date and quantity received.
- Locate the current stock: how much of the lot remains and in which locations.
- List the shipments: each order that took the lot, with its customer, dispatch date and quantity.
- Reconcile the quantities: the quantity received must equal what remains plus what was shipped, plus the recorded write-offs.
- Hold the stock of the lot in the system so that no order takes it.
- Record the end time and what was missing or slow: a document without the lot, an unrecorded return, a quantity discrepancy.
- Correct the process that caused each finding and repeat the mock recall in a few months.
If the quantities do not reconcile in step 5, the chain has a gap: a movement without the lot, unrecorded shrinkage or a shipment recorded with another lot. That finding is the value of the exercise.
Lots, expiration dates and FEFO
Traceability and rotation by expiration date use the same data. If the lot and the expiration date are recorded at receiving, the system can allocate the lot that expires first (FEFO) and reject at receiving a lot with less shelf life than the accepted minimum. The guide FIFO and FEFO explains when each rule applies.
How Chainlink WMS handles it
In Chainlink, a product is configured with tracking by lot and with Requires expiration date. At receiving, the app reads the product, expiration date, lot and serial number from a GS1-128 label and requests manual entry of any missing element. With a minimum shelf life, receiving stops if the lot expires before the accepted period («This lot expires in 12 days; the minimum accepted is 30 days») until an authorized user decides.
At picking, Chainlink allocates the lot that expires first, and the handheld confirms the lot with a scan; with the rules of Professional and Enterprise, strict FEFO does not accept any other lot. The stock ledger filtered by lot shows each movement with its date, origin and destination locations, user and document, including the outbound documents with their customer. Stock in quarantine, blocked or damaged is not allocated to any order. Returns are created from the original outbound document, with their lot, and are inspected before they are restocked, written off as shrinkage or returned to the supplier. See lot and expiration date tracking and WMS for food and beverage.
Frequently asked questions
What is the difference between lot traceability and serial number traceability?
A lot groups many units produced together; a serial number identifies a single unit. Serial number traceability is more granular and is used for equipment and high-value products. Each product is tracked one way or the other, according to what its industry requires.
How long should a recall take in the warehouse?
There is no single time limit: it depends on your industry, your customers and your recall plan. The recommended practice is to measure the time of each mock recall and reduce it. With the lot recorded on every shipment, identifying the customers is a query, not a document review.
Does a WMS certify compliance with NOM-251?
No. Compliance depends on your company's processes. A WMS provides the records by lot, location, user and time that a recall plan and an audit require.