What is a SKU?
A SKU (stock keeping unit) is your own code for each product or variation you sell, used to track it in stock, sales and purchasing.
A SKU identifies one sellable item in your own system. Each size and colour of a shirt gets its own SKU, because each is counted and reordered separately. Unlike a UPC or EAN barcode, which is assigned by the manufacturer and is the same in every store, a SKU is yours: two shops selling the same shirt will usually give it different SKUs.
A good SKU is short, unique and readable. A common pattern is category, then product, then attributes: TEE-BLK-M for a black medium tee, or CF-ETH-340 for a 340 g bag of Ethiopian coffee. Avoid letters that look like numbers (O and 0, I and 1), avoid spaces and special characters, and do not start with zeros that spreadsheets will strip off.
SKUs earn their keep in three places: importing and updating products in bulk from a spreadsheet, matching purchases to the right product when stock arrives, and reading reports by item. Many shops also print the SKU as a Code 128 barcode for items that have no manufacturer barcode, so the same scanner works on everything.
In SeroPOS every product has a SKU. If you leave it blank, the app or back office generates one, using the SKU prefix set in Business Settings, then Product. The product search at the till finds items by name or SKU, and a keyboard-wedge scanner that reads an exact SKU match adds the item. SKUs are also the key for bulk import and for matching items when you connect to QuickBooks.
A coffee roaster sets SKUs as origin, roast and size: ETH-L-340 (Ethiopia, light, 340 g) and ETH-L-1000 (Ethiopia, light, 1 kg). The 340 g bag also has the supplier's UPC printed on it, so either the UPC or the SKU finds it at the till, but only the SKU is used in the roaster's spreadsheet and reorder list.