Financial training6 min read
Which of your jobs actually make money? A one-afternoon check
How to group a year of invoices by job type and see margin for each, using records you already have and a spreadsheet.
- Updated
- 18 Oct 2026
In short
If you read nothing else.
- 01
Most contractors know whether the year was good, not which jobs made it good.
- 02
Group invoices by job type and match direct costs to each job.
- 03
Compare margin by type. The weakest type is usually the one you do most.
In this guide3 sections +
Most contractors know the year was good. Very few know which jobs made it good. The bank balance mixes everything together: the bathroom that ran at a healthy margin and the kitchen that barely covered its costs look the same once the money is in the account.
What you need
- Twelve months of invoices, or an export from your accounting software
- Supplier invoices and slips, ideally marked with the job they were for
- Timesheets or a rough record of who worked on which job
- Your overhead recovery rate, or an estimate of it
The method
- 01List every job in a spreadsheet: date, customer, job type, invoiced amount excluding VAT.
- 02Keep job types broad. Four to six is enough: kitchens, bathrooms, shopfitting, callouts, and so on.
- 03Against each job, add materials, labour hours × labour cost, subcontractors and travel.
- 04Add overhead: labour hours × your overhead recovery rate.
- 05Work out margin per job: (invoice − total cost) ÷ invoice.
- 06Total by job type and compare.
Where supplier slips are not marked by job, use the quote as a guide and note it as an estimate. Be honest about which figures are measured and which are guessed. A finding built mostly on guesses is a question, not an answer.
Reading the result
- A job type with high revenue and low margin is the most expensive thing in the business. It ties up people and cash for little return.
- Negative margin on small jobs usually means travel and admin are not being charged.
- A wide spread of margins within one job type means the quoting is inconsistent, not that the work is.
General information, not advice. This guide explains the general position for South African businesses. It is not tax, legal or accounting advice. For your specific situation, speak to your accountant, registered tax practitioner or attorney.