Your margin is only as honest as your cost. The cost book is the audit trail for one product: each change, when it happened, why, and the sum that produced it — so a row can be checked rather than believed.
- 1
Open it from the product
Open a product and go to its cost history. The Cost book lists every change with four columns: When, Why, Cost, and How it was worked out.
- 2
Read the arithmetic
A row from a delivery spells the sum out: you had 10 at 300, took in 5 at 250, giving 15 at the blended figure. That is the point of the book — you are not asked to trust a number, you are shown where it came from. A row that says Stock received came from receiving a purchase order; Opening balance is where the product started.
- 3
Switch the scope
Showing lets you look at the product as a whole or at one location. A product-level row is a blend across locations rather than one delivery, so it says "Blended across locations" instead of pretending there is a single sum to show.
- 4
Know which method applies to this product
Two methods, and the product's type decides which one — it is not a choice:
- Weighted average — everything that is not serialized. The average of what you paid, weighted by how much you bought at each price.
- By serial number — serialized products. A phone bought at 300 and one bought at 250 stay worth 300 and 250, because each unit has an identity.
- 5
Check whether costing is switched on at all
Weighted-average costing is something a store turns on, under Inventory costing. If it has never been switched on, the product carries the cost of the last delivery instead of an average — which is exactly the difference between "buy 10 at 300 then 10 at 250" ending at 275 or at 250. The costing screen says whether it is running and since when.
- 6
Read the impact before switching it on
If it is off, the costing screen shows what turning it on would change: your stock valued as carried today, the same stock averaged, and the difference — plus whether your inventory value and reported margin will rise or fall. It is worked out from the items that have enough purchase history, and it says how many of your stocked items that covers.
Proffs tips
- The cost book records the rounded value that was actually stored, so it always reconciles with the product. Over a long chain of deliveries a fraction of a cent can drift — that is accepted on purpose, because a book that matches the product matters more than the sub-cent.
- "This product's cost has not changed yet" on a product you have received several times usually means those receipts predate the cost book. New changes are recorded from here on.
Var detta till hjälp?