Labour/Kaat schemes
Each supplier on their own terms
Give each supplier one or more named labour/kaat schemes, one of them the default. Labour/Kaat can be in ratti (out of 96), per 10 g, or a percentage, and set as In or Out, exactly as it’s agreed across the counter.
Vendor wastage can be added per piece on top of net weight. The terms are copied onto each delivery line, so changing a scheme later never rewrites old balances.