A quote request arrives from a customer who would be a good name to have on the books. The price in your head is roughly what you charged the last similar customer. You are not certain what the work actually costs once labour, materials, transport and the time spent on admin are counted, but you know the competition is close and the customer is waiting. So you send a number, and hope.
That small moment is where knowing your margins starts to matter. This piece argues, as a hypothesis, that a clear view of margins changes what an owner can choose: which work to accept, which to price differently, which to decline and which costs to confront. It is not an argument that every business should chase higher margins, only that choices made without the numbers are narrower than they look.
Margin, in plain terms
Margin is the share of a sale that is left after the costs attached to it. The word is used loosely, so it helps to be exact about which one is meant.
- Gross margin is revenue less the direct cost of what was sold, expressed as a share of revenue. Investopedia's explanation of gross margin sets out the standard definition. For a service business, direct costs usually include the labour spent on the job.
- Contribution margin looks at what each sale leaves to cover fixed costs and profit, after variable costs. Wikipedia's overview of contribution margin explains how it is calculated and why it is useful when deciding whether a particular product, job or customer is worth keeping.
- Net margin is what remains after every cost, including overheads, interest and tax.
An owner does not need all three for every decision. But knowing at least gross or contribution margin by product, service or customer is what lets a business tell the difference between being busy and being profitable.
Why the numbers change what you can choose
The argument is about choice, not about maximising. Consider what an owner can and cannot do without a margin figure.
Without margins, pricing tends to follow competitors, habit or the last quote. Every piece of work looks equally attractive because revenue is the only visible number. Turning work down feels reckless, so it rarely happens. Cost increases from suppliers are absorbed quietly until the end-of-year figures show a problem.
With margins, an owner can see that one customer segment funds the business while another consumes time for little return. A price increase can be targeted. A supplier cost increase can be passed on promptly and in proportion. A tempting large order can be assessed against the capacity it would use.
That is the optionality in the title: the ability to decide, rather than react. The second element is financial breathing room. A business that knows its margins can see how far revenue can fall, or costs rise, before things become uncomfortable. For an owner who is personally exposed to the business, as is common in small South African firms, that visibility is a form of resilience.
Why many owners do not know them
Margins are not hidden because owners are careless. They are hidden because the information required to calculate them sits in several places and is slow to bring together.
- Sales are in one system, supplier invoices in an inbox, and payroll in another file.
- Time spent on jobs is not recorded, so labour cost per job is a guess.
- Reports are produced monthly, after the decisions they would have informed.
- Different people hold different definitions of cost, so figures do not agree. Mellorca's piece on when nobody can say which number is true describes the effect.
- Calculations live in spreadsheets with formulas nobody fully trusts, a risk examined in the cost of fees and charges calculated in spreadsheets.
The practical consequence is described in Mellorca's analysis of having no visibility into customer and product profitability. A business can trade for years without knowing which part of it earns its keep.
What South African tax rules add
Margins interact with the tax regime in ways that make the numbers more than an internal matter. Two examples, with a caution that thresholds change and should be checked with SARS before relying on them.
Value-added tax is charged on most goods and services, and a business whose taxable supplies pass the compulsory registration threshold must register. SARS describes the rules on its VAT page. Registration changes how prices and costs should be viewed: output VAT is collected on behalf of SARS and input VAT may be claimed, so margins should be assessed on figures excluding VAT. A business that mixes the two can believe it has a healthy margin when part of it belongs to SARS.
Turnover tax is a simplified regime for qualifying micro businesses, described on the SARS turnover tax page. It taxes turnover instead of profit, which changes how an owner should think about costs. Whichever regime applies, knowing your own margin makes it easier to judge what the tax bill means in practice.
An illustrative scenario
Consider a hypothetical example, not a real business: a Cape Town company that fits and services commercial refrigeration, with nine staff. It does three kinds of work: new installations, scheduled maintenance contracts, and emergency call-outs. Revenue has grown steadily and the owner assumes the business is healthy.
When the bookkeeper finally gathers technician hours, parts costs and vehicle running costs by job type, the picture is uneven. Installations are profitable but irregular. Maintenance contracts are priced the same way they were three years ago and, after fuel and labour increases, barely cover their direct costs. Emergency call-outs carry a premium and leave the largest margin, but the small team cannot take more of them without neglecting contracts.
Armed with this, the owner has choices that were previously invisible. Maintenance contract prices can be raised at renewal, with the reasons explained. A minimum call-out charge can be introduced. One low-margin contract that needs a long drive each month can be declined or repriced. None of these decisions is guaranteed to be easy or popular, but each is now a decision rather than a drift.
Getting to a usable margin view
This does not need a finance department. It needs a few agreed definitions and a rhythm.
- Pick the level that matches your decisions. By product, by service line, by customer, or by job. Start with the one where you most often price or decline work.
- Agree what counts as direct cost. Materials, subcontractors and the labour hours spent on the work. Write the definition down so figures stay comparable.
- Capture time, even roughly. Labour is the largest hidden cost in service businesses and the one most often missing.
- Exclude VAT consistently. Margins should be worked out on figures that belong to the business.
- Update more often than yearly. Quarterly is a sensible start; monthly if prices or costs move quickly.
- Keep one agreed source. Margins that differ between the owner's spreadsheet and the accountant's report undermine confidence in both. See the freedom that comes from knowing where things stand for what a single trusted picture feels like.
The human dividend
The dividend is optionality and breathing room. An owner who knows their margins can say yes, no or not at that price with some confidence. They can plan a quiet month, see a cost shock coming, or decide to invest. For staff, it can mean steadier work and fewer panicked weeks when cash runs short.
The trade-offs
- Margin figures can mislead. Allocating overheads is a judgement call, and a low-margin job may still be worth doing if it brings steady volume or leads to better work.
- Measuring takes effort. Capturing time and costs costs time, especially at first.
- Pricing decisions have human consequences. Raising prices or ending an unprofitable arrangement affects customers and sometimes long relationships.
- Precision can be false. A figure to two decimals built on guessed inputs is only as good as the guesses.
- Margin is not the whole of purpose. Some owners accept lower margins deliberately, for community, craft or values reasons. Knowing the number is what makes that a choice.
Why it matters
Choices are only as wide as the information behind them. An owner who does not know their margins is not free to ignore them; they are simply making the same decisions with less light. Knowing the numbers does not decide what to do, but it shows what the options are, and it allows a business to keep what it values for reasons it can see.
Sources and further reading
- Contribution margin - Wikipedia (last verified 10 October 2026)
- Value-Added Tax - South African Revenue Service (last verified 10 October 2026)
- Turnover Tax - South African Revenue Service (last verified 10 October 2026)
Related Mellorca reading
- When Late Invoices Become Late Salaries
- The Cash-Flow Week That Keeps the Owner Awake
- The Owner Who Can't Decide Without the Spreadsheet Wizard