Serial and lot numbers are the two ways to trace stock below the product level. A serial number identifies one unit, such as one phone; a lot number identifies a batch made together, such as one day's yoghurt. A serial tells you who bought this unit, and a lot tells you where this batch went.
This guide compares the two and shows which goods need which. It works a recall and a warranty claim in Uganda shillings, and sets out how to record both in ArmPOS.
What is a lot number?
A lot number, also called a batch number, is a code shared by every unit made or packed together. Codex, the international food standards body, defines a lot as "a definitive quantity of a commodity produced essentially under the same conditions".
For example, a soap maker that turns out 1,000 bars from one mix gives all 1,000 bars the same lot number. If that mix was wrong, the lot number finds every affected bar without checking the rest.
Lot numbers suit goods made in runs and judged by the batch: food, drinks, medicines, cosmetics, seeds and farm chemicals. Many carry an expiry date beside the lot number.
What is a serial number?
A serial number is a code given to one unit and to no other, even among identical units from the same batch. Two laptops of the same model look the same, but each has its own serial number.
A phone's serial number is its IMEI, a 15-digit number the phone shows when you dial *#06#. The GSMA, the mobile industry's association, tells owners to note it because, if the phone is stolen, "this can help your operator block the device".
Serial numbers suit goods sold one by one that a customer may bring back: phones, laptops, televisions, fridges and power tools. GS1 Nigeria notes that a product number plus a serial number identifies an individual item.
Serial vs lot numbers: the differences
A serial number follows one unit, and a lot number follows a group. Every other difference in the table comes from that.
| Feature | Serial number | Lot number |
|---|---|---|
| Identifies | One unit | One batch of units |
| Units that share it | None | Every unit made or packed together |
| The question it answers | Who bought this unit, and when? | Where did this batch go? |
| Recorded | For every unit, when it arrives and when it sells | Once per batch on each delivery |
| Used for | Warranties, repairs, returns and theft | Recalls, expiry dates and quality complaints |
| Typical goods | Phones, laptops, appliances, tools | Food, medicines, cosmetics, chemicals |
| Where it is printed | On the unit and its box, often as a barcode | On every pack, often beside the expiry date |
A product can carry both, when each unit must be traced and each batch recalled. GS1 South Africa notes that its barcodes can carry serial numbers, dates and batch numbers alongside the product number.
Which goods need serial numbers, lot numbers, both or neither?
Track serial numbers when one unit is worth chasing, and lot numbers when a fault or an expiry date hits a whole batch. Each costs a scan or an entry every time stock moves, so goods that need neither should get neither.
| Trade | Track | Why |
|---|---|---|
| Phone and electronics shop | Serial numbers (IMEI) | Each unit carries its own warranty, return and theft risk |
| Appliance and power tool dealer | Serial numbers | Warranty claims come unit by unit |
| Pharmacy | Lot numbers with expiry dates | Recalls and expiry come batch by batch |
| Supermarket or mini-market | Lot numbers with expiry dates, on perishables | A supplier's recall names a batch |
| Cosmetics and beauty shop | Lot numbers with expiry dates | Products go off, and are recalled, by batch |
| Agro-dealer: seeds, fertiliser, chemicals | Lot numbers | A bad batch of seed or spray is traced by its lot |
| Hardware and stationery | Neither, unless an item carries a warranty | A product code is enough |
| Clothing and shoes | Neither | Sizes and colours are variants, not batches |
Goods tracked by lot and expiry date should leave the shelf in expiry order, the rule set out in first expired, first out (FEFO).
For example: one recall and one warranty claim
The two numbers pay at different moments: a lot number when a supplier recalls a batch, a serial number when a customer brings something back. Both cases are illustrative, in Uganda shillings.
A recall at a supermarket
For example, a supermarket in Kampala holds three batches of one yoghurt at UGX 3,000 a pack: YG-0412 (60 packs), YG-0415 (80) and YG-0419 (100). The supplier recalls batch YG-0412.
| Line | Without batch records | With batch records |
|---|---|---|
| Packs taken off sale at once | All 240, until staff have read every pack's code | The 60 from YG-0412 |
| Value taken off sale | 720,000 | 180,000 |
| Value that keeps selling | 0 | 540,000 |
| Where the batch sits | Unknown until each shelf and store room is checked | On the batch list, by warehouse |
| Who to claim the credit from | Whoever staff remember | The purchase and the supplier the batch came in on |
The batch record turns a shelf-by-shelf search into a decision made before anyone touches the shelf. The other two batches keep selling while the recalled one waits for the supplier.
A warranty claim at a phone shop
For example, a phone shop in Kampala sells a phone for UGX 650,000 on 10 January, with a 6-month warranty. On 2 August a customer brings back a phone with a dead screen and asks for a free repair.
The IMEI settles it. The shop's record shows the unit was sold on 10 January to that customer. The warranty ended on 10 July, 23 days before the claim.
Without the record, the shop can't even tell whether the phone came from its own stock. It either pays for the repair or argues with no proof.
What the rules say
For packaged food, the rule is a lot mark on every container. It comes from the Codex General Standard for the Labelling of Prepackaged Foods. Each container shall be "permanently marked in code or in clear to identify the producing factory and the lot".
For medicines, Nigeria has gone furthest. Since 2024 it has required GS1 standards on the labels of all pharmaceuticals. The Director General of NAFDAC, its food and drug regulator, says so in a GS1 case study.
NAFDAC's traceability system, built on GS1 standards, has already handled a recall. When a COVID-19 vaccine batch was found compromised, NAFDAC found every place it had been distributed in under an hour. The physical return took about a week.
Rules differ by country and change, so check your own food and drug regulator's current rules. Serial and lot records are also one of the controls that keep stock honest, with the rest set out in inventory control.
How to track serial and lot numbers in ArmPOS
ArmPOS tracks serial and IMEI numbers unit by unit, and batches with their expiry dates, each switched on product by product. Switch serial tracking on before the stock arrives: units already in stock can't be given serial numbers later.
Serial numbers and IMEIs
- Switch it on twice. In Settings › System Settings, tab Feature Toggles, switch on Track Serial Number / IMEI. Then switch it on under Options on each product (Serial numbers and warranties).
- Set the warranty. Under Warranty & Guarantee Tracking, set the Warranty Period and the terms. Each sale's warranty ends on the sale date plus the period.
- Record each unit on the purchase. Enter Serial Numbers / IMEI opens on the line: scan each unit, paste a list or import a file. The count must equal the quantity, and each number can exist only once in the shop.
- Pick the unit at the sale. Select Serial Numbers / IMEI opens at the POS, and Pay Now waits until each unit sold has its number. The receipt shows it as IMEI/SN.
- Find any unit. Products › Serial Numbers lists every unit with its status, supplier and customer, and History shows each move.
- Check a claim. Sold Serial Numbers shows who bought a unit and when, and the Warranty / Guarantee Report shows the days remaining (Serial number and warranty reports).
Scan these numbers rather than type them, for the reasons in how barcodes and QR codes reduce human error.
One limit matters for shops with branches: transfers, adjustments and damages don't move serial numbers. Sell serial-numbered goods from the warehouse they arrived in, or move them with a purchase return and a new purchase.
Lot numbers and expiry dates
- Switch on Track batches & expiry in the product's Pharmacy Settings. For stock already on the shelf, Opening Batch & Expiry assigns its batches (Batches and expiry dates).
- Enter each delivery's batches on the purchase: Batch No, Expiry Date and, if you have it, Manufacturing Date. A line left without a Batch No is dropped, and that stock can't be sold at the till.
- Pick the batch at the till. Choose batch lists each batch with its expiry date and quantity, the one expiring first at the top.
- Act on a recall. On Products › Batches, set the batch's Status to Quarantined to keep it out of every sale. If the goods are destroyed, Write Off removes what is left, with a reason; how the loss reaches the books is in inventory write-off.
- Trace it back. Reports › Batch Register lists every batch with its purchase and supplier, and opens each batch's full history (Stock reports).
ArmPOS doesn't stop a sale past the expiry date, and doesn't mark a batch expired by itself. Check the Expiry Report often, and quarantine or write off expired batches yourself.
The steps are the same in every country ArmPOS serves, from Uganda to Egypt.
Frequently asked questions
What is the difference between a serial number and a lot number?
A serial number identifies one unit; a lot number identifies a batch made or packed together. Many units share a lot number, but no two share a serial number.
Is a lot number the same as a batch number?
Yes, in everyday use the two mean the same thing. ArmPOS calls it the Batch No.
Is an IMEI a serial number?
Yes: it identifies one phone and no other. ArmPOS records it with other serial numbers, under Track Serial Number / IMEI.
Can a product have both a serial and a lot number?
Yes. A unit can carry its own serial number and its batch's lot number, so it can be traced alone and recalled with its batch.
Does a small shop need serial or lot tracking?
Only for the goods that need it. A phone shop needs serial numbers and a pharmacy needs lots, but a stationery shop needs neither, and tracking them would slow every sale.
Pick the products where a recall or a warranty claim would cost you most, and track only those. To record serial numbers, batches and expiry dates from the first delivery, create a free ArmPOS account. The Starter plan is free, with no card needed, and the pricing page shows what each plan includes.
