The number to watch
Yield per lot. A block or a container of slabs arrives at a landed cost, and what you actually sold out of it after cutting, breakage and wastage is the only figure that tells you whether the lot was worth buying. Most stone dealers know their selling rate to the rupee and have never worked out yield on a single lot. Recording purchases with freight included and sales against the same lot gives you that number without any extra effort, and it usually changes which sizes and which suppliers you buy from next.
Three units, one invoice
A dealer supplying a house sells slabs measured in square feet, cut pieces by the piece, and sometimes a block by weight. Doing that on paper means three different calculations while the customer watches, and any of them can be wrong in your favour or theirs. With the unit held on the item you pick the material, enter the quantity and the arithmetic is done — including where the same stone is stocked in one unit and sold in another.
Wastage, and putting it in writing
Every stone trade works with a wastage allowance, and every dispute about a bill starts with it not being written down. Show the measured quantity and the allowance as separate lines rather than folding one into the other. The customer sees exactly what they are paying for, and six months later so do you. It also means your own consumption figures are honest, which matters when you are working out what a lot actually yielded.
Lot-wise stock and matching
Stone from different lots does not match, and a customer who returns for two more slabs six weeks later expects the same shade. Keeping each lot as its own item — with its own rate and its own stock — is how you answer that question without walking the yard. It also stops the common loss where a premium lot is sold at the rate of an ordinary one because both were entered as "granite".