How the margin is calculated

Three numbers per pool and per month, and every one of them can be traced back.

Where each number comes from

Revenue — the agreed service price valid in that month, net. From the service price; a change supersedes, so the month is calculated with the price that applied then.

Material — from the stock ledger. Every visit records what was used, and each amount is valued at the price per unit that applied on that day. Changing a price later does not rewrite past visits.

Labour — from staff cost and working time:

• hourly → duration of the visit × rate × on-cost,
• daily → day rate ÷ the number of stops that person did that day,
• monthly → not calculable. Spreading a monthly salary needs the hours actually worked, and those are not recorded. An assumed 160 hours would be a claim about utilisation that nobody has checked, and it would shift every margin by the same factor.

What is deliberately missing

Travel. It is not in the figure, and the result is named accordingly: contribution before travel. The cost per kilometre exists per vehicle, but getting from a vehicle to a single pool needs the route's kilometres split across its stops, and routes do not reliably carry their distance.

Shortfalls are not attributed to a pool. Shrinkage belongs to no customer — it would make somebody look expensive who had nothing to do with it. It has its own list and its own total.

What it does not do

It does not gross up. A pool with three visits in a four-visit month is calculated with three, not with an assumed fourth.

It does not allocate overhead — office, software, insurance that is not on a vehicle. What you see is the contribution towards those, not a profit.