MorningA technician takes a filter off the shelf for a car on a ramp. He means to write it down. He is holding a filter.
MiddayThe counter sells the last two of the same filter, because the figure still says three.
AfternoonThe job is invoiced. The filter is charged at whatever the service advisor thinks it costs, which is last year’s price.
FridayA garage on account collects parts. The delivery is written in a book and invoiced at the end of the month, from the book.
Month endJob profitability is a guess, the counter margin is a different guess, and the stock figure is wrong in a way that will take a full count to find.
What it actually costsMargin measured against a price nobody has paid since last year
The fix is that a store issue is a document, exactly like a sale is a document. Once both post, the shelf and the figure stop drifting and job profitability becomes a fact.