# Serial numbers and warranties

> Track each unit by its own serial number or IMEI from delivery to sale and back, and set the warranty each sale starts.

*Section: Products and stock · Updated: 2026-10-19*

By the end you will know how to track each unit of a product by its own serial number or IMEI, from the delivery to the sale and back, and how its warranty is worked out.

Serial numbers suit things sold one by one that a customer might bring back: phones, laptops, appliances, tools.

> **Note:** The demo shop doesn't sell serial-numbered goods, so the purchase and sale steps below were written from ArmPOS's screens and code, not run.

## Switch it on

1. **Open [Settings › System Settings](/app/settings/System_settings), tab Feature Toggles,** switch on **Track Serial Number / IMEI** and **click Submit.** This makes the option appear on products.
2. **Open the product** and, under **Options**, switch on **Track Serial Number / IMEI.** Click **Save Product** or **Save Changes**.

![Feature Toggles: Enable 3 Decimal Pricing, Enable Kitchen Display (on), Show Product GTIN, Serial Numbers / IMEI with Track Serial Number / IMEI, Multi-Pack Selling, Automatic Journal Entries (on) and Offline Sync (on).](https://armpos.online/storage/help/428132768c-serial-numbers-and-warranties-1-setting.webp)
*The shop-wide switch only adds the option to products: each product still needs its own.*

> **Warning:** Switch tracking on **before** you receive the product. Units already in stock have no serial numbers, and ArmPOS has no way to add them later, so the till can't sell them.

## The warranty

Under **Warranty & Guarantee Tracking** on the product's form, set the **Warranty Period** (a number, then **Days**, **Months** or **Years**) and the **Warranty Terms**. Switch on **Has Guarantee** to add a **Guarantee Period**. This works with or without serial numbers.

Each sale then gets its warranty end date: the sale's date plus the period. It shows in the **Warranty / Guarantee Report**, not on the receipt.

## Receive the units

On a purchase, a serial-tracked line opens **Enter Serial Numbers / IMEI** with a counter, **Serials: n / qty**:

- Scan each unit's barcode, or type the number and press Enter.
- Or paste a list (one per line, or separated by commas) with the clipboard button, or import a CSV or Excel file.

When the purchase is **received**, the number of serials must equal the quantity, and each number can exist only once in the whole shop. Each unit is then **Available** in that warehouse.

## Sell a unit

At the POS and on **Add sale**, the line opens **Select Serial Numbers / IMEI**: scan the unit, or tick it in the list of available units in that warehouse. **Pay Now** waits until one serial is chosen per unit sold. The receipt and the invoice show it as **IMEI/SN**, and the unit becomes **Sold**, linked to the customer.

## Returns

- A **sale return** lists the serials sold on that sale; the returned unit is available again in the return's warehouse.
- A **purchase return** lists the units from that purchase still available; they become **Returned to Supplier**.

## Find a unit

**[Products › Serial Numbers](/app/serial_numbers/list)** lists every unit with its **Serial Number**, product, **Warehouse**, **Status**, **Supplier** and **Customer**. Search by number, or filter by warehouse and status. **History** on a row shows the unit's every move: when it was bought, sold and returned, by whom, with the reference.

![Serial Number Management: Search this table, Warehouse and Status filters, and the columns Serial Number, Name, Warehouse, Status, Supplier, Customer and Action.](https://armpos.online/storage/help/948c8fb9a2-serial-numbers-and-warranties-2-list.webp)
*Search a serial number to find who bought the unit and when.*

On a unit's page you can mark an available unit **Damaged** or **Reserved**, and back to **Available**.

> **Note:** Transfers, adjustments and damages don't move serial numbers: a unit moved to another warehouse that way can't be sold there. Move serial-numbered goods with a purchase return and a new purchase, or sell them from the warehouse they arrived in.

## What's next

The reports for serial numbers and warranties: [Serial number and warranty reports](/app/help/serial-and-warranty-reports).