Trade Approved calibrations to are calibrations that are legal for vendors to use to sell goods based on weight.
Thus as an example - if you are selling apples based on case (NOT weight) but need to weigh the apples for freight requirements then the scale does not need to be Trade Approved
If though you are selling apples in a case but based on the kilograms of apples within this case then you are required to have a Trade Approved scale.
Whilst the difference between a non-Trade Approved scale and a Trade Approved scale may seem hard to fathom as the products may look identical. A Trade Approved scale has been through a rigorous testing process to ensure that the scale will read valid weights anywhere on the deck of the scale. This gives your customers confidence that your scale is capable of accurately measuring a weight when an item is placed on it.