Lot and serial number tracking: who got which batch?

It is 4:40 on a Friday afternoon when the quality lead opens a short email from a supplier: a raw material batch delivered eight months ago has failed a conformity check, and everything made from it needs to come back off the shelves. The email contains exactly one usable piece of data, the supplier's batch number. She turns to the warehouse manager and asks how many units came out of that batch, how many shipped, and to whom. Three hours later six people have lined up their own spreadsheets and produced 41 shipments, except that two of them cannot be tied to a batch at all and one delivery note has the number field left blank. The figures here are illustrative; the point is that you pay for those three hours and those two blank rows in the middle of a crisis, at the worst possible exchange rate.

This article treats lot and serial tracking not as a labelling habit but as a chain of evidence you can walk backwards from a shipment. We start with the difference between the two identifiers and how to decide which products deserve which. Then we cover where a number is born, what the links in the chain are, where the chain usually snaps at the packing bench, how to sequence outbound movement for dated goods, what to do in the first hours of a recall, and how to handle returned stock. The last sections cover the measurements that prove the system works and a thirty-day rollout. If you operate in a field where traceability is legally mandated, have the design you end up with reviewed by your own regulatory adviser; what follows is method, not a substitute for sector rules.

Are lots and serial numbers the same thing, and which suits which product?

A lot is a set: items made under the same conditions or received in the same delivery, all represented by one number. A serial number is an identity: one number, one physical object. The gap between them is not just resolution, it is accountability. With lots, when you say "everything affected by this number," you mean the whole set. With serials, you know which specific unit went to which customer, how many times it came back for service, and when its warranty ends.

The useful question is not which is better, but how a defect propagates. If a mix goes wrong, every unit from that mix carries the same risk, so set logic is enough. If one board in a thousand has a bad solder joint, the set is innocent and you need individual identity. Plenty of operations run both: the product is made under a lot, and the higher value variants also get serials. We covered the inventory side of these definitions in the piece on serial and batch tracking; here the focus is how that identity travels all the way to the customer.

Which products should carry a number, and which can stay untracked?

Numbering everything sounds prudent and behaves like friction. Every tracked line means one more scan at receiving, one more match at dispatch, and one more breakdown at stock count. Narrowing scope deliberately at the start is far better than ending up in the position where you track everything and trust nothing. Decide scope against concrete criteria rather than instinct.

Decision criterion	No tracking	Lot is enough	Serial required
How a defect spreads	Isolated, limited consequence	The whole production or delivery set is affected together	Each unit behaves independently
Warranty and service	None, or settled by swap	Set level replacement is enough	Per unit service history required
Shelf life	None	Yes, date belongs to the batch	Yes, plus per unit documentation
Unit value	Low	Medium	High
Shipping volume	Very high count, low risk	High count, limited number of batches	Low count, high expectations

Do not fill the table once and file it away. Revisit scope quarterly: a line sourced from a new supplier, a variant whose complaint volume is climbing, or a product going into export for the first time can all move from untracked to tracked in a single quarter.

When is a number born: at receiving or at production?

Every number needs one birthplace, and only one. For goods you buy and resell, the number is born at receiving: the supplier's batch reference is captured on the inbound line, and if you maintain internal numbering, the two are stored as a mapped pair. For goods you make or repack, the number is born on the way out, and the component lots that fed it are recorded in the same moment, because nobody reconstructs that later from memory.

Labels belong to that same moment. Recording a number in software while someone writes it on the carton with a marker weakens the first link on day one. In Rocketly, Label and Barcode Printing produces product labels as barcodes or QR codes in a print ready PDF, so the warehouse scans instead of typing and transcription errors disappear. Barcode and SKU is the layer underneath: one SKU per item ends the familiar mess of the same product living on two cards under two names. If your item master needs cleaning before you number anything, the groundwork in setting up inventory management properly comes first.

What are the links that tie a batch to a customer?

Traceability is the product of a series of records, not of one screen. The chain runs: goods receipt, warehouse and bin placement, order reservation, dispatch document, invoice, customer ledger line. If any link does not carry the number, that is where the chain breaks, and in a recall you are left with a list of customers who "probably" received it. The rule is blunt: the number is written at every event where goods physically move, and never inferred afterwards.

In Rocketly, Stock Movements keeps receipts, issues, transfers and reservations under immutable record; when something is wrong the original line is not deleted, a correcting movement is appended. For traceability that matters more than it sounds, because the story of where a batch came from and where it went can only grow, never be rewritten. Delivery Notes and e-Delivery Notes tie the shipment to a document, while Stock Deduction from Invoice drops stock in the same transaction when you invoice directly. Whichever flow you use, the document that performs the deduction is the moment the batch becomes attached to a customer.

The last link sits in the ledger. Whoever received the shipment is also where the receivable accumulates, which makes joining batch data to the customer record the shortest path to a contact list during a recall. Keeping customer account records in order means the answer to "who did we sell this batch to" is already assembled before you need it.

Where does the chain usually snap during dispatch?

It snaps in the warehouse, under time pressure, in four familiar places. First, split shipments: half the order comes from one batch and the rest from another, but the paperwork carries a single number. Second, kits: the customer receives one line item that contains three components from three different lots, and none of the component numbers are captured. Third, unit confusion: an item shipped by the case is converted to eaches incorrectly, so quantity and batch record stop agreeing. Fourth, haste: the number field is left blank with the intention of filling it in later, and later never arrives.

All four share one remedy: a shipment must not be able to close while the number field is empty. A system that stops you is more reliable than a person who remembers. For bundles, the Kit / Set Product logic works from component stock, so component level records make the lots inside a kit visible; Unit of Measure Conversion lets you define alternatives like cases and packs while stock stays in a single base unit, which stops quantity and batch records from drifting apart. There is a physical discipline too: keep different batches out of the same bin, and if that is not feasible, organise placement by batch rather than by bin.

How do you sequence outbound movement for dated goods?

For anything with an expiry date, the right order is not arrival order but date order. First in, first out fails as soon as suppliers deliver stock with different remaining shelf life: a long dated batch received two weeks ago will ship ahead of a short dated batch received yesterday, and the short dated one dies on the shelf. FEFO, first expired first out, fixes that. In Rocketly, Lot / Serial Tracking provides traceability by batch and serial along with FEFO issue by expiry date and a list of items approaching expiry, so the sequence is not left to whoever happens to be picking that morning.

Turn the approaching expiry list into a weekly ritual. Each line has three possible outcomes: ship it first, discount it and clear it, or write it off. Delay is the most expensive of the three, because value erodes quietly every day. The discipline is the same one you apply to any dated instrument in the business: decide in advance what happens as the date approaches. The habit behind tracking dated payment instruments transfers directly to shelf life.

What do you do in the first hours of a recall?

A recall is a sequencing problem, not a software problem, and the sequence matters. First, freeze the batch: remaining stock under that number becomes unshippable and reservations are released. Second, scope it: how many units were made or received, how many sold, how many sit in the warehouse, how many are in transit. Third, build the customer list from dispatch records, with quantities per account. Fourth, communicate; the same message reaches everyone on the same day, because staggered notification destroys trust faster than the defect itself. Fifth, open the return channel and write down where the goods go, how, and at whose cost. Sixth, log everything you do while you do it.

The scoping step depends entirely on how easily you can get data out. Bulk Operations and Export exports movements as CSV or XLSX in the background, and Background Job Tracking shows queued, running, completed, failed or cancelled status with a progress percentage, so you can close the browser and the job keeps going. That is how you avoid hearing "the report still will not download" in the middle of a crisis.

Communication generates call volume, and the same questions repeat. Logging which objection came up how many times sharpens the script you will use on day two; the method behind spotting recurring objections in calls does the same job in crisis communication. If you are subject to mandatory notification, confirm who must be told and within what window with your own regulatory adviser.

What happens to returned batches, and can they be sold again?

Returned goods should never land straight back in sellable stock. They belong in a physically separate quarantine area and, in the system, in a separate warehouse so nobody can ship them by accident. Every quarantined batch ends with one of three written outcomes: inspected and released, reworked and released, or destroyed. Who decided and on what date belongs in the record, because a verbal decision becomes an unexplainable gap a few months later.

On the record side, a return is the mirror of a sale. In Rocketly, Customer Return Entry ties the return to its sales invoice and only converts the quantity actually shipped into a stock receipt, so a quantity that never left the building cannot be added back. Whether the paperwork calls for a credit note or a correction depends on the case, and knowing the routes for cancelling and correcting invoices in advance saves you from improvising per customer during a bad week.

Recalls also hit collections. Some invoices for the affected batch will be unpaid, and some customers will suspend payment on purpose. Do not let those lines sit in the same queue as ordinary lateness; tag them separately, or your process for chasing overdue invoices gets contaminated with crisis noise and the genuine credit risk becomes invisible.

How do you prove your traceability actually works?

The honest test is a drill. Once a quarter, pick a batch number at random and start a timer: how many minutes, and how many separate records, does it take to answer where those units went? The second measure is scope accuracy: when you compare the list you produced against physical reality, do you find missing or extra rows? The third is the gap rate: across the last three months of dispatch lines, what share had an empty number field? Without writing these three down you cannot see improvement, only feel it.

The fourth measure is agreement between the books. Stock and Accounting Reconciliation lists records that were invoiced but never deducted from stock; a growing list means batch data is also incomplete, because a sale with no stock movement cannot be tied to a batch. When these figures go to management, put them on one screen, and let the role based logic behind dashboard design decide who sees which number.

One warning: traceability metrics turn into self deception easily. "Ninety percent of our products are tracked" says nothing if the untracked ten percent is where the risk lives. Reading what a chart measures and what it quietly excludes is a separate skill, and the habits described in reading reports critically apply here too.

It also helps to know where your own bookkeeping ends and your accountant's work begins, since that boundary determines how traceability data reaches the statutory books; the split between the two is worth being explicit about.

What does the first thirty days look like?

Do not attempt the whole thing in one move. Week one is scope: run the table above against your own item list and write down which lines get lots, which get serials, and which stay untracked. Week two is birth: make the batch field mandatory on the receiving screen, print labels, and teach the warehouse one rule, that no carton reaches a shelf without being scanned. Week three is the outbound side: dispatch documents cannot close without a number, and kits record component lots. Week four is measurement: run a drill, calculate the gap rate, and list what is still missing.

At the end of thirty days you will not have a perfect system. You will have something better, a setup that can start from a batch number and reach a customer list, and that knows exactly which of its links are still weak. If you would rather build that in one place, with receiving, movements, dispatch and invoicing sitting on the same record, that is the shorter route: open a free Rocketly account and run your first scope decision against your real item list.

FAQ

What do I do with existing stock when I switch to lot tracking?

Retro numbering what is already on the shelf is usually wasted effort, because you cannot prove which batch the physical goods came from. The common approach is to record the opening quantity as a single transition batch, note explicitly that it carries unknown provenance, and start real numbering from the next receipt onward. Once the transition batch is consumed, your tracking is genuinely clean.

Does serial tracking slow down shipping?

Typed, yes. Scanned, no. The delay does not come from the number, it comes from how the number is captured. A scanned serial adds a couple of seconds to packing; the same number written on paper and keyed in at the end of the day multiplies both time and error rate. Keeping scope tight also keeps the cost small.

What if my supplier does not give me batch numbers?

Generate your own internal batch: each goods receipt becomes a batch in its own right, with supplier, date and purchase order attached. That is less precise than the supplier's production batch, but it still lets you walk back to a specific delivery. Asking for batch references on documents at contract renewal is the medium term fix.

Who should run the recall drill?

Someone whose day job is not dispatch, because the person who built the process cannot see its blind spot. A practical arrangement is for someone in finance or quality to pick a batch at random and put the question to the warehouse. Record the elapsed time, the records consulted and the gaps found on a single page. That page is the starting point for the next drill.