Do I need a trade approved scale?

If the scale weight reading is linked directly to a financial transaction then yes you will need a trade approved scale. Although most commonly seen in retail stores where the weight is directly multiplied by a price per weight unit to achieve a total price, trade approval is also required in pre-pack or factory applications when packing goods into packages with a stated weight. If pre-packing to a nominal weight, ie a 5 kg bag of product, then a trade approved would most likely be required. As a rule of thumb it is always prudent to check with your local trade measurement authority regarding your particular application to ensure you make the correct equipment selection.