From a quote to an invoice

Most workshop software makes you copy a quote into a job card and the job card into an invoice, and the three drift apart. MOTION carries one document the whole way. What you priced is what the mechanic works from, and what the mechanic worked on is what the customer is billed for.

The stages

1. 1Quote — a price, before anybody has committed to anything. It holds a number as soon as it is raised.
2. 2Booking — a day in the diary. Still a draft; nothing has been done yet.
3. 3Job card — the car is in. Mechanics clock on to this, parts come off stock against it, inspections hang off it.
4. 4Invoice — the work is finished and priced. Processing it is the moment the money becomes real.
5. 5Credit note — where an invoice has to be given back, in part or whole.

What processing actually does

Up to the moment you process, a document is a draft: you can change anything on it and nothing has left the building. Processing is the commitment. It stamps the number, takes the parts off stock, and puts the amount onto what the customer owes.

A processed document can never be edited. That is deliberate — an invoice somebody can quietly change is not evidence of anything. If it is wrong, void it and raise a new one, or credit it.

Why the tax on an old invoice does not change

Each document keeps the tax name and rate it was raised under, stamped onto it at the time. Changing the workshop's tax setting today has no effect on anything already raised. That is what lets a period spanning a rate change show both rates and still be correct.