Jobs is every piece of work you have done or have booked, with the detail behind each one: the customer, what was done, what was used, and what it was invoiced for.
What the detail is for
A job record in a field service system answers "what happened". The same record next to your accounting data answers a harder question: was it worth doing.
That requires three things to be attached to the job rather than to the month — the materials, the labor, and the invoice. Where all three are present, margin per job is a fact. Where any is missing, it is an estimate, and usually a flattering one.
The habit that makes this work
Cost the job, not the month.
Materials bought on a Tuesday and filed against "materials" tell you what you spent. The same materials attached to the job tell you which work is profitable, which is a different and far more useful answer. It is the same data entry either way; the difference is where it lands.
Labor is the one most often missed, and the one that changes the answer most. A job with materials costed and hours ignored will always look profitable.
See job costs.
From one job to the pattern
A single job's margin is interesting. The pattern across a job type is actionable — that is job margins, and it is where the common uncomfortable finding shows up: the work that fills the schedule is often not the work that carries the profit.
Jobs you record here
Work your other systems do not carry can be tracked directly, with its own materials list, expenses and invoices — see job costing.
Where jobs come from
Jobs sync from your field service system. Creating and updating them happens there; this is where they meet the money.